Maybe she wants an illusion of a happy family with you and your kids since her own kids aren’t in the picture.

I am a stepmother and my husband is a stepdad. I can’t imagine harassing stepkids in this manner like demanding pictures or gifts? I am a step grandma too but little one calls me grandma and my stepdaughter treats me as I am grandma (not step) but I still am not in their face like that. It’s ridiculous. I I don’t think I ever even ask for pictures. Or demand excessive get together or anything. Not at all

As about being one sided. My sister in law is this way. She usually doesn’t attend our events but expect us to attend hers.

Honestly the only advice I have is keep interactions to a minimum. Short. Infrequent. I think it’s ok for kids to see obnoxious relative. Kind of teaches them about life. But make it very minimal. That’s what I would do.