Struggling with DD

[unclestripe]

I have 2 DD's, one is 4 months and one is just turning 4 years.
Im really struggling with DD (4) behaviour, Its been like this for a while but it's recently (say the past month) got so so much worse. I absolutely understand that a lot of this is likely caused by her sisters arrival but I cannot continue like this and need some advice on how to deal with the behaviour.
Some days she's fine, a lovely little girl, loves to help, plays nicely, full of love and cuddles. Other days it's like she wakes up a different child, she goes out of her way to get a reaction and finds it hilarious when she's doing something she knows she shouldn't be, if she's told not to do something or moved away from whatever it is she'll scream, hit, punch, slap, bite, kick all while in a kind of giggling frenzy.
No kind of discipline or gentle parenting approach works.
I've tried distraction, she just fixates on whatever it is she shouldn't be doing and continues.
I've tried time out in her bedroom by herself, she just starts destroying her things, time out while sitting in her room with her, she gets physical and hits, kicks, punches.
I've tried simply moving myself away, she just follows and continues.
Nothing gets through to her and I usually end up shouting which I hate.
She gets daily one to one time with both myself and her dad to make sure she isn't feeling left out, we try to include her as much as possible in whatever we are doing with baby.
I've spoken to her nursery that she attends two days a week, they don't see the same behaviour there.
I'm honestly at a loss with what to do, I feel like our relationship is starting to be affected, she tells me I'm a bad mum all the time, and I'm just mentally drained. Help.

When you say that it's got worse in the last month, has anything happened, like an infection?

@SiouxsieSiouxStiletto She had a sickness bug around 3 weeks ago for a couple of days but nothing other than that

I don't think it's PANDAS from what you've said, it's quite rare fir one thing but definitely read the article and see what you think.

If it's not PANDAS could ASD be a possibility?

@SiouxsieSiouxStiletto Thankyou for taking the time to answer me. I have never heard of that, it was an interesting read. She does actually present with a few of the other symptoms listed particularly the bed wetting/day wetting, she has been toilet trained since 2 but started having frequent accidents a couple of months ago. She is also often very hyperactive and struggles to concentrate on tasks that she used to be able to and wakes most nights at least once. I can't recall her ever having symptoms of strep throat though and if it was PANDAS would it not be a constant thing? She's not like this in nursery although does have accidents there.
Asd had crossed my mind but again I thought that would be something that was present all the time. I have reached out to the HV but she just put it down to normal child behaviour adjusting to the arrival of a new sibling which wasn't very helpful.

If it is ASD she's very likely to mask at Nursery, which doesn't help you I know.

Could you ask to talk to the Nursery's SENCO and see if they'll have a proper look at her?

I'd be tempted to call the HV and let her know that you're struggling and ask her to do the 4 year Ages & Stages.

@SiouxsieSiouxStiletto yes I hadn't considered masking, I think I will do that when she is in nursery tomorrow, even if it isn't it's worth exploring that avenue I suppose.
I did have a look at the 4 years ages and stages questionnaire and she's meeting pretty much all of it bar 1 or two so I'm not sure if that would make a difference.

How is her communication and her ability to name or describe her feelings? I'm wondering if you could try asking her how she's feeling, either during one of these episodes or afterwards, when she's a bit calmer. You might need to do a bit of 'I wonder if you were feeling frustrated/angry/whatever you think it might be'. When she's calm, she might also be able to say what would help her to try.

I also wonder if when it's happening it's partly a need for lots of stimulation. As you describe, it sounds like she's feeling wild and crazy, rather than, say, being very angry. Perhaps when that happens, something like a game of tickle monster (if she likes being tickled) or chase-and-hug could give her what she needs? Let her do some of the chasing, as well. Or maybe some bouncing on a trampoline, if you have one, or dancing to some noisy, bouncy music? If there's an element of needing to be contrary, I saw a suggestion once of a game where you say 'yes' loudly/softly/squeakily/etc. and then they have to say 'no' in the same way, going through as many silly voices as you can come up with.