Any other stepmoms? I have a situation/rant:

BM (biomom) and my BF have a week on/week off schedule, exchanging every Sunday. The problem is BM is ALWAYS late and the last two times BM brought SD (stepdaughter, 2 years old) over she had a severe diaper rash and cried when I had to put diaper rash on her. BM said "yeah she must've pooped really bad in the middle of the night"...no, this was much worse. On top of that she always pawns off SD onto us on her weeks because she is either "too stressed" or "too busy" or SD is being sassy and BM can't "handle it". My BF doesn't want to "stir the pot" by telling her to get her shit together or we'll go for full custody. How would you handle it?