What is the point of a porn star (even a fake taxi girl, a C-list star) if they say 'no' to reasonable requests? No thanks.
But on a small point from the OP, there is no reason to think a porn star will have big, loose pussy. It is a muscle, not a hole to be drilled into. Wanking does not make your hand big, does it? Actually, girls who have a lot of sex (and take care of pelvic floor muscle, with Kegel exercise) can be the tightest.