I completely agree with the other ladies! Granted you COULD suck it up for the big day, but the problem is it's not just one day it's a whole week - your wedding week at that. (which should be the week of your life, if I may add!!!) I should probably just bite my tongue on this one but if she's generally an attention seeker than she's going to be jelous that you and your man are getting all the attention so she may try and steal the spotlight....if you know what I mean (that sounded worse than what I meant....) For some people that wouldn't be a big deal, but when she already irritates you than it's just going to make it worse, and in turn you wont be enjoying yourself to the fullest - which you completely deserve! By the sounds of it your FI at one point was close with this person but that is no longer the case, seeing that you only see her and her husband once a year it really shouldn't be a huge problem she doesn't attend the wedding. Not to mention that if she was unpleasant to you and your family in the past than she shouldn't be there as far as I'm concerned. This is a time to bring your two families together, not make them uncomfortable because of a rotten egg hanging around. Maybe I'm just being harsh but I don't have any sympathy for people like that.
The guestlist is definately a touchy subject though!!! LOL Luckily my FI really doesn't care who comes as long as we have a good time and there's NO drama! Which should be interesting since his family isn't a fan of my family (or me for that matter...) - we will be having a chat with them before we go about there "I'm better than you attitude" and hopefully things will work out!