My 8 yr old hates wiping her own butt

💢💢 Please No Bashing Or Rudeness. Rude or Argumentative Comments Will Be Deleted & You Will Be Reported For Being A Bully💢💢 okay I have been in my Bonus Daughters life since she was 2. I potty trained her with her dad and everything. Ever since she started school she's been wiping her own butt but I'd go and check behind her to make sure she did a good job. well I stopped doing this after she got better at it and when she entered the 1st grade at age 6. She would never ask for help UNLESS she was sick and it was one of those kinds of poops that is hard to get off. But little did we know that Every time she went to her Grandmothers she would go and wipe her before she would even try to wipe herself. We even have explained to her that she is 8 and can do it herself but she spoils her to much & continues to wipe her instead of making her do it herself. She is 8 & This is ridiculous. She knows how to wipe and she knows when she has done a good job but she recently spent 2 wks away from us at her BioMoms house then she also spent 3 nights with her Grandmother. She came back to us being bratty with an attitude & is refusing to wipe herself and gets very hateful with us mostly me when I don't go in there an wipe her. We just don't know what to do anymore expect not let her go over to her grandmothers but that is apparently "Mean of us to do." As her grandmother has told us. Please Help 😢