Hmmm, could she be doing it cause she's in competition with you? Chances are she knows you mind and wants to get to you by doing this. Yr boyfriend, being male, possibly doesn't realize its a form of manipulation on his daughters side!
my toddler broke her leg in two places from climbing up an indoor slide and jumping off. Now recovered, she still wants to slide and I fear this could happen again. What can I do to keep thisfrom happening? Kids love to play and are rambunctious.
No you are not overreacting. There is more than just father and daughter relationship there, I wouldn't say it was sexual, just intimate, which it really shouldn't be. If it was that way before you started going with your boyfriend, then a choice has to be made by him. It is time to be unfimiliar with his daughters sex life and start dating you, or you dump him. I assume he gets sexually aroused with her on his lap. And if he does then his daughter is not oblivious. A choice has to be made!