Aibu to say this is theft?

Yes its theft. Your DH is a nob.

Undamaged clothes should be returned. You should reimburse your eldest for the clothes that have been damaged as you are responsible for your 13 yo. Consequences would include her paying you back over time by stopping pocket money or doing chores. I would also be taking the phone for a period of time. Is your 13 yo remorseful. I would be concerned that she thinks this was ok.

"That kind of "gentle parenting" is the reason so many kids become entitled little brats"

Not the time and the place , but that is NOT "gentle parenting".

Sure there is a need to understand. There is also a requirement here to learn a lesson. And that will best be served if there are consequences.

So not living in school uniform - but definitely having to miss out on fun stuff in favour of earning the money to pay the sister back.

The daft DH needs to learn that lesson too. So i suggest he pays the older DD the cost of replacements, and works out how to get the money back off younger DD.

i mean it wasn't a serious suggestion but why the emphatic no?
The little pest needs to learn. Some kids learn better when they have the same done to them

13 is the age of criminal resonsibility so the police could get involved. However, making her replace the clothes and apologise would be more effective. A near brush has more power. (The police would probably just put the fear of god and incarceration up her.)

Explain to your dd that you are within your rights to call the police and she needs to tell you why you shouldn't AND, more importantly, what she is going to do to make things right. That way you've done restorative justice and your dd has learned her lesson.

Then tell her she needs to keep her word and you will forgive but not forget. That way, if there's a repeat you will come down harder.

Hopefully that will work. Her actions were inexcusable but kids are stupid.

Why are you letting your 13-year old parade stolen outfits on TikTok??
Yes, it is stealing and yes she definitely needs to feel the consequences of that. But you also need to give your head a wobble with regards to boundaries and 13-year olds on social media.

Correct.

She hasn't "borrowed", she has taken her sister's property and damaged it such that it cannot even be returned to her sister.

A conversation is clearly not enough - this girl KNOWS she's done wrong and the only way to prevent her repeating such behaviour is for there to be consequences which she doesn't like. Her sister's things need to be replaced at HER expense to start with.

This is not just borrowing between siblings, even unauthorised borrowing, as the older girl doesn't live at home and the clothes were packed away in a case, clearly being taken away with her.
I also think that using the term “nicking” minimises it.
This is theft and the intention was clearly “permanently to deprive”, as the garments were altered by the younger sister, to suit her.
(Technically, it is also burglary, because the girl entered part of a dwelling she was not authorised to enter and stole.)

Therefore I think that the younger sister should be made to know in no uncertain terms that, in the outside world, she would end up being branded a thief and a criminal, which would affect her life prospects.
I would hope that the disappointment in her for her family would also affect her.
Punishment? Perhaps, as the seriousness of her actions should be emphasised.
But certainly reparation to her sister, until the clothes are replaced, apologies and hopefully, realisation and remorse.

As for Tik Tok, I wouldn’t think it advisable to let a teen go on it, for all the reasons we know, but certainly because it seems to have egged her on to steal clothes, in order to perform.

The strange thing is that the crime wasn't discovered until the Tik Tok videos (which shouldn't be allowed at 13, FYI)

If eldest daughter's story is true then the only culprit was her younger sister unless your husband has a penchant for wearing teenage girls clothing

I disagree with your h. It’s one thing to borrow clothes and quietly return them but damaging someone else’s clothes on purpose isn’t typical sibling behaviour. Your older dd has every right to be furious about her sibling’s devious and destructive behaviour.

I would tell dd2 to work out how to make it up to her sister eg dd2 packs and pays postage to dd1 and pays money for damaged top so dd1 can buy another.

My sister used to do the exact same kind of thing with my stuff. When I would go to grab something off her, she would shout "Mum, peakygold gave me jeans/earrings/jewellery box and now she's taking it back". And mum would reply "peakygold, you can't take back something you have given". Of course your youngest must be punished or else your eldest DD will hate you forever, believe me.

What's she's done is awful.
But no parent in their right mind would make their child wear their school.uniform all the time 🙄

As other PPs have said this was a spiteful and malicious act - and suggests it was both targeted at DD19 and that your DD13 needs counselling. The fact that DH is not willing to issue consequences communicates that he neither cares enough about DD13 to respond/act, nor about DD19 to offer her support. Both DDs will find their self-esteem damaged by this, which will only feed what ever is happening between the two girls at present.

Is DD19 being ‘bigged up’ at home for doing so well at Uni, holding down a job, for being independent - and is this upsetting DD13 who does not feel valued or seen (hence the TikTok displacement focus where she may feel she is meeting these needs)? Do you need to look at what is going on in DD13s life (school, friendships) and reassure her of your high regard - is she doing well at school, does she play a team sport etc? Are you positively reinforcing her when she is doing well?

However, re the clothing, DD13 must suffer the consequences - loss of smart phone/SM; repayment of the cost to replace the clothing (ideally by a protracted working off the debt so she understands how hard it was for DD19 to earn it), and she needs to apologise (sincerely, perhaps once the impact of the consequences has done its magic). However, I think some family centred counselling (group and individual) is needed of you are to get to the bottom of this and rebuild both your DD’s self esteem hereafter.

Is your younger daughter remorseful at all? It’s an awful thing to do especially as your older one worked hard to earn the money to pay for the stuff!

is it normal for a 13 yr old to be making TikTok’s presumably showing off their tummy if they have altered the top to do that? Not sure I would be happy about my daughter doing that (she’s currently quite little so have all this to come!)

This.

It is stealing. She went into a packed case knowing that her sister was taking these clothes with her and that makes it very sneaky.

she needs to apologise (and mean it) to her sister. i would also tell her she needs to not only pay for the replacements but also find them (online or wherever) and get them so that older sister isn’t inconvenience and hopefully it will be a nice boring tedious task for her

I would suggest to her that she can get a paper round, or she can do chores whether that’s qt home or for the wider family/neighbours to earn the money.

Tell your dh the normal sisterly clothes robbing is nicking a top for the night, hope you don’t get caught snd putting it back next day. Not what the 13yo did .

you need to find out why she did it, as it was pre meditated. remove TikTok, she pays for clothes and apologised

I think the fact that she ripped the tops pushes this very firmly into a more serious incident. It shows she had no intention of returning the tops and a complete disregard for her sister's property. She should absolutely be punished!

Tbh I am surprised that dh is so keen to minimise dd2's behaviour - does he favour the younger dc?

I have three teenage daughters - 13, 16 and 18. I would be horrified if one of my daughters did this. It's not normal sibling behaviour and definitely needs dealing with. I agree with the punishment suggested by @PieAndLattes . Your eldest was understandably very upset and you need to support her in ensuring this doesn't happen again.