Step mommy issues

I'm a step mom to two beutiful kids that I live with full time the mom sees them once a week for a couple hours. I provided for them cook clean love them like their my own, and tomorrow I have to meet her. I hear nothing but horror drama stories about her and I'm just getting such bad anxiety about it. I want to be the better person and introduce myself shake hands but I'm worried. I'm also pregnant do my mind is going crazy. If any of you step moms have gone through this how did it go?