Advice!!!!!

I need advice. My SIL asked what days I was available in October for baby shower. I gave her 4 days. That was two weeks ago. She is now asking about a totally different day. I will be just a few days shy of 37 weeks which is why I don't want that date. My OB has said I may go into labor early due to how early my husband and I both were. He was 3 weeks early and I was 2.5 weeks early. I really don't want to wait that long so much so I started crying talking to my mom (yes I know it's hormones but they aren't going away anytime soon). My mom said I don't have much choice. My husband told me to tell her that I'm busy that day. I just don't understand why she couldn't do a day I suggested.

Anyways how would you address this? I wanted al my showers in September now all will be in October. 😰 honestly we thought they weren't even going to throw one since they waited until two weeks ago to even ask me about it.

UPDATE: I just want advice on how to turn her down. Not get people pissed at me because I'm having two and that I'm not comfortable with it that close to my due date.