Hi, this may be a bit late to add, but:
All the family need to take the worm tablets. You need to treat the whole family because one of you may have it and not know, or it may be getting passed along with the eggs in different reproductive cycles. So everyone takes the drugs, and repeats too. Wash all bedding, towels and underwear/pyjamas, at the hotted you can.
Plus nailbrushes and antibacterial washes.
My DS had worms when he was about 6. But that was because he was playing in the mud in the school fields, as you'd expect from a 6 year old boy. However, your DD is 12. Where is she getting the eggs from, do you think? Does she do some activity where she is in contact with soil or other places where she may be getting the eggs into her mouth -this is usually through the fingernails I think. She could be just reinfecting herself in the home, or it's being passed along through family members. Or through a close friend.
Have a look online at where the eggs live, and think if she is coming into contact with them.
Good luck. Horrid. Ugh! Poor DD.