I'm confused about whether she will actually be in *your* room or not. Or did you reserve a block of rooms or something and she would have one of those? When you say "The one last spot in our rooms" it's confusing. So there is one last spot.....would you be OK if someone OTHER than her was in it? If so, that's sad.....
I'm with Gamma G, she's his mom, not some cousin or friend. It is nice that he wants to pay for her, i would say it's even nice that he puts her on a pedastol somewhat.....don't you hope YOUR son will treat you the same one day?
If your husband already offered to pay for her, he can't back out of that now....that would be super tacky and hurtful. He will simply have to find a way to pay for it. If it's not in your family budget, I guess that will mean him working a second job for a month, or whatever. But I wouldn't step in after the fact and make him go back on his offer to his mother.
I mean really, I have a 2 year old son who I love beyond life itself and some of the posts on here from women complaining their MIL's make me depressed. "She used to visit us for two weeks at a time, I put a stop to that." Wow....is that what I have to look forward to when my son gets married.....great.....
I really think moms of daughters have an easier time of staying closer after they get married....because husbands tend to be so much more laid back about in laws, than wives. I wonder if YOUR mom would be welcome to stay for 2 weeks....(probably) and if your husband would "put a stop to it" if he didn't like it....probably not....he would probably just deal with it b/c he knows it's important to you. Meanwhile, so many wives seem to have a "no tolerance policy" toward their husband's moms.
I see you have a son too so it's just something to think about.
ADDED: I see your "So what happened."....saying she "runs your husband ragged" and is "attached at the hip" when she sees him....well that's probably b/c she doesn't see him too often (it sounds like she's not local)....for goodness sake, I'm sure she loves her son, misses him, and wants to spend time with him! I have a girlfriend who complains about the same thing....they only see her husband's mom once a year if that and then she complains that "She wants to go with us every where we go" during the trip....ummmm yeah.....she wants to spend time with her son....HAVE A HEART LADIES!