Issit wrote:
Maybe you can take a mobile phone or a tablet..or a comp with you,
and just distract yourself surfing the net most of the time or playing games.
The group will not mind I bet.
Bigger groups do not really care about individuals who do not want to socialize.
In this case, I think it would be perceived as rude & dismissive of the in-laws. They are wanting this opportunity to get to know her & for her to tune them out & blow them off like this would make a very bad impression. Been there, done that, got the reputation for being a stuck up b***h.
I agree w/the poster that pointed out such a large number of people will break up into sub-groups & amuse themselves. You won't be under the microscope of 18 people all at once. It'll be one or three at a time. And fluid.
I usually stay pretty close to my partner when I am in groups like this. I am comfortable w/her, so that's automatically one person that's not difficult.
And because she knows me, she deals w/the bulk of the conversation & supports me if I want to participate, smooths things over along the way. Maybe you could do that?
And I've found that a lot of folks understand if I just say I'm a bit of a hermit & so many people, tho' fun & interesting (compliment them; make clear it's not because you don't like them) is pretty overwhelming & you need some quiet time. It's [mostly] true. Of course, out of 18 people there will be some you can't stand, but there's also a good chance there will be one or two you really enjoy.
Good luck!