Family basically falling apart

Take away the 14 year olds phone/ipad, then you won't need to mess around changing the wifi password. She has to then earn it back.
No criticism from me - it's hard being the only real parent and having no support network to advise and help you. But you need to say what you mean and mean what you say to the 14 year old - no threats that you cannot carry through. You absolutely must not cave under her pressure. Actions have consequences, so you cut off her access to the things she values most until she proves she's mature and kind enough to deserve them.

Is there a possibility that they could attend different schools? It would give each dd personal space and relief for your 17 yr old. If not, can school give any wisdom on what's going on or provide some wellbeing intervention?
Maybe investigate family counselling.

Talk to both girls individually - see if you can get to the bottom of dd 14 behaviour - see if there's any bullying or social issues amongst friends which could be exacerbating the situation.

If it consoled at all, my youngest dc was absolutely mean to on of her older brothers as a child/young teen. She obviously preferred her other older siblings and was just awful for no reason to the one other dc. She eventually grew out of it and they are very close now, so kids can and do change.

OP I'm just going to jump on and say I get how hard it is when you're an SP and it's all on you and it's relentless hostility in your own home with no back up. I don't disagree that you need to be more assertive but I'm guilty of letting things slide too because sometimes you just can't keep going. All good advice on here about WiFi passwords, accepting that the 14yo will be awful in response but there you go and so on but I just wanted to say I get why you might have got to this point. Sending a hand hold. You might want to try the teenagers board too..it's a little less brutal than AIBU.

You teach them that certain words, tone of voice and behaviour isn't acceptable at home. At the same time, how they talk to their friends isn't your concern!

Believe me, both my DC can swear pretty badly - they had a phase where it was cool amongst their friends. But they know it's not acceptable to do at home. Home language is polite and respectful. Talking to teachers is polite and respectful and talking to their friends is whatever they choose!

Another vote for you not doing anywhere near enough to parent your 14yo. I know it’s not what you wanted to hear but this is entirely within your control and you are full of excuses because parenting her properly isn’t convenient. If you bothered to do it, you’d realise how much easier it is than what you’re doing now! It may sound like the hard option but, if you follow through, you’ll realise it’s not.

1. If she steals from you and DD(17) then get locks on both your doors and remind DD(17) to lock her door when you leave the house. Now DD(14) can be left alone at home - no, not for a week, no one suggested that and nor did you mention a week until the excuse-making started.
2. Don’t turn off the wifi, change the password. Do not give it back until her behaviour improves. If she is rude, stronger consequences. Why is she still going on camps and events? She’s a mean, rude, thief - my mother wouldn’t have allowed me within a mile.
3. Take her phone and laptop. There’s no reason to block the wifi if she can hotspot from her phone. Do you really think making her internet access just slightly slower is an appropriate sanction?
4. Every single action needs a consequence. Every time she is rude, slams a door, swears, kicks off - you take another item. She doesn’t need more than her school uniform and a pair of pjs left in her room.
5. No more “disapproving looks”… do you think the police give disapproving looks to criminals? Does it work? Ridiculous. You say firmly, and loudly, “do not speak to your sister that way. I am now removing X until you behave appropriately” and follow through.

Most teens don’t behave like the 14 year old. I do think all kids have a point where they are challenging though and actually if it’s at primary school then they may well be less difficult later. Compliant children get to 14 and realise they actually dont have to do what they are told. Less compliant ones worked that out when they were little and may have already worked through it.

OP you need to sort the 14 year old. In fact the 17 year old can be left on her own for several days and may well enjoy the peace. It may give you the chance to get to the bottom of what’s going on and why her self esteem is so low she is putting her sister down all the time.

Tbh if I was the 17 yo I would prefer to be left at home not going on a holiday being bullied by the 14 yo with my mum accepting it.

The point is it’s not pleasant or enjoyable to eat as a family currently.. the suggestion is to have time with each of the girls, one at a time, to determine what’s up. And then also try meals together.
For a longer trip away you’d of course go together.

I agree with PP that it seems you have a discipline and understanding problem with dd14. Her acting out - both cause and effect need addressing both through conversation and more effective punishment like removing WiFi, withholding pocket money, additional chores etc.

No, you can’t go out for lunch as a family.

And you can’t go on holiday without them going to their dads.

Your oldest hasn’t done anything, it’s your youngest who is pulling the family apart. What does she says when you talk to her about the way she behaves towards her sister?

Sisters don't get along but when they get older they might surprise you. Hiw were you about the sibling relationship in their early years, did you encourage them to love and tolerate each other then?

Exactly!

Why would you want to go out for lunch as a family when you know your 17 year old is going to be treated so badly?

I have a similar dynamic with sibling and mother. Mother would vaguely tell sibling off but not want to upset her so would be woolly about it and expect me to put up with it. I have very little contact with either of them now and will never see sibling again once mother dies.

Is that the future you want?

Are you here for help, or did you just want a whinge?

Because if you want help then you'll have to listen to people. What you are doing is not enough, you are much too passive. You need to read the book I suggested and change how you are speaking with your DDs if you want the outcome to change.

Yes its extremely hard dealing with a recalcitrant teenager as a single parent. I do t know why people are being so sparky!

You aren’t parenting your 14 year old.

I feel very sorry for your older child.

Well you can, but it doesn’t seem to be working well. What people are suggesting - and I agree - is that until the 14 year old starts behaving better you have one-on-one time with each daughter rather than taking them both out and having a miserable time. The older one will enjoy spending time with you without being bullied by her sister and the younger one might actually open up to you about what is making her so unpleasant.

I will, thanks 👍🏼

Maybe next time you assume that people are contributing outside of their experience based only on the fact that it doesn't match yours you could tone the passive aggressiveness down a bit?

You’re not being hard enough on your 14 yo. You’re allowing her to be a bully! Why??
if she won’t behave better you should leave her out of things and enforce better boundaries. Take her phone etc. It’s not easy being the youngest but this is no way to behave.

What’s the situation with their dad OP? Could this be causing her some distress?
When did this behaviour start and has it been a change? What’s her situation like at school? Friends?

@ThePhantomoftheEcobubbleOpera good for you give yourself a pat on the back for being so amazing!

I have two teens, 18 and 16 and neither of them have thrown the house into chaos by being a general shit, by being obnoxious to one another or stealing from, well anyone let alone from their family.

But you said the trips were for lunch or short day trips. I leave my 9 year old at home for ten minutes; surely a 14 year old could be left while you go out for lunch with her sister?