Example #24305967487 of why its very difficult to have friends of the opposite sex.
If she couldnt understand why her staying there while the wife is away then
I think whats irking her, is that she would totally open up her house to me if I made the same cross country trip to have a weekend of just watching football, drinking beer, and eating.
And rules like "no guests of opposite sex while spouse is away" is what turns her off to relationships in general. So I can see her side of "WTF, I'm flying to see my brother (essentially) and I gotta stay in a hotel?!"