from your two questions I can tell you this: you are looking for someone to read your mind, only probably want them only to read what you want them to read and not the other stuff. Am I close? This may be also connected to whatever relationship problems you have
Why are you asking such vague questions? You might as well use a magic eight ball to get your answers.
Your sister sounds very insecure. It is clear that she has feelings for your child's father and is attempting to act on them by innocently asking him to attend events for her child while pushing you out of the picture. She sounds like she is an attention seeker and clearly doesn't care about who she hurts in the process. I think you should talk to your sister about her behavior because it bothers you evidently. I also think that she is kind of immature for sneaking around with your child's father behind your back.
Hypnotize her. You will find the answer...
No, seriously...maybe she just wants attention. Can you elaborate a little bit more on what happened? As in when it started, is your sis o drugs, etc. Background info tells alot. Maybe just seek legal advise...$ Do you have full legal custody of your child? If you dont...get it now! (this is coming from a 14 year old, only child, who had similar but quite different probs.)
better question why have you and rest of family not whip her ***?
She hates you more than she hates him.
Maybe she senses what you've been doing with her husband all along. So maybe you should be the first to tell her before her husband does...then blames youy for making the first pass at him. Cause asure you it will come out and you'll look like the bad guy. So be the good guy first clean your slate and blame everything on him. You will upset anger her. But diffrence is you'll gain a sister back her trust and confidence in you for being honest and riding yourself of guilt. If not she will get your husband and many others involved. Hurry before time runs out. Then you two can get a place together and leave your creeps!
what is she doing?
No clue since we don't understand the full picture.
A little vague for an honest answer...