I agree with Kaz.

I would just stop trying. After all, making her say sorry is not making her feel sorry. I try not to make the girls say sorry. But it's hard for me. Especially when they've done something to another kid and I fell like they should say sorry. But I'm trying to remember that it's more important to me to teach empathy than manners iykwim. So instead I will just try to draw attention to what they've done and how it effected the other person. E.g. if DD1 hurts DD2 I might say 'Poor DD2, look at her, she's crying, that must have really hurt her' and more often than not DD1 will then come over and try and make her feel better. Mission accomplished

HTH!