Yeah, she's miffed about the birthday party and suddenly feeling that you're keeping her at arm's reach, or maybe your husband doesn't like her, or whatever else may go through a woman's mind when they're already upset and feeling slighted.
Etiquette for a birthday party invite would be at least 1 week, preferably 2, to plan on it, especially if you live an hour away. How often has your family been invited to her family's dinners? No, I don't do that very often. I love doing lunch with my friends, but dinner is often our family wind down after a hectic day. When we do "do dinner", it does tend to be a single mom with 1 child, a couple neighbors or coworkers with no children, that kind of thing. Because I am a little protective of the boys' night time routines. We do have fight nights but again, the only people that come with children would be our neighbors.....and their children are each 1 year older than my children, so the mom leaves early to get her children ready for bed when my children are getting ready for bed. And with my bff, I treasure that time to talk and be together, so I want it to be without children. And I'd tell her so.
I had a friend that I was SOOOO excited was coming back into town after not seeing her for a decade. She moved back to town, and we had all kinds of ideas on how much time we'd hang out together. But it didn't happen like that at all. They are much more strict, aren't interested in things we love (concerts, gardens, museums, roaming around downtown, water parks, etc) but love nascar and football. The end. But not "hey, let's run by the highschool game for cheap entertainment and watch the marching bands"....it would have to be NFL or nothing (and they had no money for NFL, so it was....nothing). Meh. Then she started invited her family over to my house for dinner. I was like "Um......ok? I had one 2 year old child then. She had a husband, and 4 boys ages 7-12. Yipes! That's a lot more food than I was comfortable with. Then "I don't like spicy. __ prefers chicken over steak. I don't like chicken on the bone. __ doesn't like dairy or cheese. ___ doesn't eat vegetables or fruit. ___ will eat rice but not pasta. etc, etc, etc." I was like "Dude. No. That's too hard for me to figure out." She's like "Oh no we're easy!" and I'm like "for what? a chicken burger with no cheese?" (blech) I said "I don't know how to cook without seasonings" and she said "Oh, __ loves spices!" and I said "Well, ok.....what spices does he like, and I'll see if I can figure something out".....her answer, no lie was "He likes all of them! Salt, pepper, ranch, catsup." They never came to our house for dinner. That was stupid. I didn't appreciate being pressured into it, either. Friendships aren't supposed to be "hard".
I'd tell her you were sorry about not coming to the party, but your husband was just really tired and drives all the time, and that was a work day and just a long end to a long day for him (it should have been a weekend anyway, if working people are invited). Tell her to meet up for lunch, because it's simpler....and that when people do come to your house, they are just a couple people from down the road. It's just different. She's an adult, so she should be ok with that. If not, it's too "hard" for me!