Ok so this sounds bad but bear with me.

We're supposed to be attending a 40th birthday party this coming Saturday for my step mum. My wife's mother had surgery last week to remove part of her lung due to a tumor. This is obviously major surgery and she's still recovering from it now. We've spent a lot of time at the hospital with her keeping her company but not much else.  

As for my mother in law's condition, she's not great. She's got a tube draining her lung and is subsequently not very mobile. She's also in some pain because of the tube. Having said that, the medical staff are confident she'll be discharged on Monday and with the tube gone quite a bit of her self sustainance will return. She's also been making marked recovery aside from a slight set back yesterday.

Now, having said all that, my mother in law also has other people who could support her, including her husband. These guys are a little further away from the hospital than us (an hour as opposed to our 30 mins) so my wife isn't the only person helping out. My sister in law is also flying down over the weekend to help out.

On Monday this week, just after the surgery, I told my dad that my wife wouldn't be able to attend. But then after that, as my mother in law began to recover we agreed my wife would be able to make it after all. After my mother in law's recovery stalled a little though, my wife now thinks she should stay.

Here's what's getting me: she isn't actually physically helping her mum, at least she's not doing anything that others couldn't do, her mum isn't in any danger of suddenly getting worse, her mum has plenty of other people to look after her but here's the kicker: _we'd only be gone for one night_. I simply can't understand why she feels she has to stay. Am I the asshole for not getting this through my thick skull?

Caveat: there's something to be said for her not feeling like partying very much, which I do understand of course, but I'd like focus on the whole mum being sick aspect as I'm trying to determine if my feelings about that Vs the party are assholish, not if she should come to the party strictly speaking.