N/C for this.
Sympathy, I have had issues with DD (also 11), don't know if they are behind us.
I don't have the energy to get very angry about it, I'll freely admit.
I take an amends approach: she's done wrong so needs to do amends & once amends are done then we draw a line under it & move on. So in your situation it would be a case of 1) apology to me as the injured party, 2) being forced to talk about it & what was going thru her mind, & to listen to me talk about it (restorative justice), 3) paying £ back (maybe with some interest), and 4) possibly some other "work", like doing chores for free that might normally be paid. It's the same idea when courts impose community service orders as a punishment for criminal activity.
I hate mine having lots of sweets, too, but I don't understand why you are trying to stop her spending pocket money on sweets, I think that (waste) is a rite of passage she needs to get on with.
If it's any comfort I was a bit of a klepto myself at about the same age, sneaky enough that my parents only caught me once. I outgrew it. Similar with lots of other silly things I tried (ie, drugs).
With BFF, DD was caught trying to nick sweets in corner shop. She didn't have the street-smarts to lie about her name & phone number, though, so shopkeeper was able to contact me. I had DD apologise in person & in writing, plus she was docked £5 pocket money which we gave to the shopkeeper (who put it in a charity box). DD also wasn't allowed sweets or pudding for a month.
Worst thing for DD was the BFF became DD's spiteful mortal enemy for 6 weeks, although eventually relations settled into civil pleasantries. Not likely to ever be close again, though. I doubt DD is completely cured of her stealing impulses, but the whole family knows what she did. I think embarrassment & potential unintended consequences (like loss of a BFF) might be enough to have finally cured her. I have also talked calmly about criminal records, and what an incredibly unforgiving age we live in. She gets a caution for shoplifting now, & there are jobs she'll never be able to get, and she could have to explain the caution in many job applications for the rest of her life (like if she went into teaching). I think she might finally be just about mature enough to grasp why that's so very undesirable.