What do I do with the cat?!

I'm not sure what to do with the cat over christmas...
She'd be fine here, I guess, but she'd be on her own for maybe 3/4 days, and I can get friends to come feed her etc, but I have an uneasyness about it - I'm not sure why. I've not left her fro more than 2 nights before, and I guess I'm worried about her getting lonely.
My Christmas Family have cats, but they also have a dog and I'm not sure if I can even think about taking her with me.
She can't go into a cattery, its way to expensive, plus she's old and isn't up to date with her vaccines etc so they wouldn't take her even if I could afford it.
She could possibly go with Allan, but she's not really his cat, so it's not that fair. If she goes somewhere/with me, what if she pees all over the place?!But she might do that here anyway, being on her own for ages.

Dang it I don't know what to do!