Leaving 2 month for a week for 21st in Vegas

My SIL is having her first child in April but told everyone at thanksgiving that her friends have already set this all up for her and she’s going to go. No one from her side of the family is watching the baby due to their reasons and my boyfriend and I couldn’t due to the fact I’m due in June. He’s worried about his first niece and I’m looking for some reassurance it’ll be okay. We know she will be drinking and will probably smoke pot while there, but how long after the trip would she need to wait to be able to breastfeed if she even is doing so? Has any other mothers left their young babies for a bit? If so did you bump extra before hand to use afterwards?