D.S.
The mother obviously feels threatened by your presence in her daughter's life for whatever reason. Some people are unreasonable and you should just ignore the woman as best as you can. My thought is that braiding her hair was not a big deal...but if there is a disagreement with the father and mother about how the child is groomed - you would do well to just stay out of it and not touch her daughter's hair. It is basically between him and her. Being a step parent is difficult. Yes, you are and will be a mother figure but you are not and should not consider yourself as such. I am on my second go around as a step parent and have learned that you can love the child and be supportive but it is best to stay out of the disagreements between parents. My daughter stayed with her father for the summer last year and his long term girlfriend called me to ask if she can take my daugter for a haircut and get her ears pierced. I was very impressed that she called me to ask first. It showed that she respected my authority as the mother and showed me how much she cared for my daughter. This might work....to show her you respect her as the Mother (even if you don't agree with her methods). It might make the relationship less volatile. You have to try something different as what has been happening in the past doesn't seem to be working. I think it is better than fighting and spending money and time in court.