I feel absolutely horrible about this situation

I’m planning my sisters bachelorette. Because it originally got postponed, and postponed again there’s been a million different dates thrown around.

I had sent out a poll but no date worked for all the bridesmaids. I then texted them and we threw out some dates but when I asked if everyone if they had suggestions or were ok traveling no one but one bridesmaid S answered saying she’ll travel.

I spoke to my sister who eventually just picked a weekend and a place and had me book it. I think at this point she was fed up with the no answer(even if they were not comfortable they could have separately said no)

My sister then sends me an email to send them all and a few friends invited. Two bridesmaids and all friends say yes so we book flights 3 days after my email.

Eventually hear from the other girls after my sister messaged one bridesmaid. S gets back to me and basically told me that that she’s fine traveling but that weekend was unfortunately the one weekend she couldn’t do. It’s a big holiday in her family and her dad passed away this year unexpectedly so it’ll be hard celebrating this first holiday without him. She hasn’t decided what to do yet(obviously doesn’t wanna leave her mom alone on the holiday) and said she’d get back to me. Basically she’d be coming home on that holiday around 2 pm.

I tell my sister and she immediately feels horrible but with the flights already booked we can’t really reschedule. My sister is going to speak to her.

Whats the best way to respond? I feel absolutely horrible about it. I feel like as a MOH I should have realized that was a weekend S couldn’t do. I don’t know if S said that weekend doesn’t work or not. I searched the holiday in texts and emails but nothing came up.