Dealing with the mother-in-law

So im not sure how many of you have to deal with this. But does anybody have a mother-in-law (or boyfriends mother) that you just really clash with...I've been with my partner for 4 years now, we're basically married as we've pretty much decided we're going to get married eventually, we just dont have the money to do the whole wedding crap and we want a house first anyway since its more important.Well my partners mother is literally the complete opposite of what i am. I'm very laid back, relaxed, chill, easy going, open minded and accepting of anything. She on the other hand is a control freak, attention seeking, demanding and difficult. My partner knows how difficult she is, and he knows i dont get on with her much. I play nice, do the round of smiles, go through all the pointless generic chit-chat with her when were around etc... But she just irritates me as everything she does is calculated to make her seem better or get attention.Today, i woke up with a pretty big headache, my father-in-law rings up telling us that shes been in a car crash, obviously we were concerned but shes not injured or hurt or anything but the car is damaged, not her fault, someone drove into her. Basically the dad asked (demanded) us to come see her as shes "shaken up by it" (we've seen the pictures of the car, its literally just the wheel arch is smashed in).Since its not serious or anything, i told my partner to go as its his mum but i'd prefer to stay as my head is pounding, its a Sunday, its a 1 hour drive to theirs and i have a pretty tough week at work ahead of me so i'd rather stay at home and get this headache sorted.Basically, their whole family has been 'summoned' to come see her (shocker... milking a small incident for attention, who would have thought) and some comments have been going around about where i am, my partner told them i'm not feeling the best with a bad migraine but his mum said "I could have died, does that not matter to him?"I'm livid, absolutely livid. Am i in the wrong here for wanting to stay home and get this headache sorted? Should i feel guilty for not wanting to see her? When we first heard she was in a car crash, i said "Where are they? ill go get changed" as i was ready to drop everything and help, but as soon as we found out shes fine, i feel like its okay to just be happy that shes fine and worry about other priorities?If it was my family and my mum, all it would require would be a nice 10 minute phone conversation, asking what happened, asking if shes alright, and all my family would be happy and fine with that. No need to rush over and see her because we all understand there is nothing serious going on.