What do you think about me no paying for my sister-in-law to join us on Spring Break?
Does your brother want you to pay for her to come on vacation with you?
Yes, my brother loves hanging out with her.
It's understandable that you don't want to pay for your sister-in-law's portion of the trip. It's pretty rude for your brother to put you in such an awkward position by asking you to foot the bill for his wife. Talk to your brother, and see if he can help pay for the trip.
Husbands and wives share everything. Why would he pay for her share of the trip when she brings down our vacation bills.
Your brother should never expect you to pay for his wife's vacation, it's rude and seems like he's taking advantage of you. Be assertive and let him know how you feel, you are not responsible for another adult.