Bit late on this one but I have to say I agree with others about the gender issue. Chick/babe just seem to conjure up images of busty bimbos for some reason, so much so I don't feel I want to be compared to one, if that makes sense...Female biker sounds a bit stand-offish. Lady biker, bit too formal and girl biker too patronising. Biker will do me!
And I agree with Grunty when it comes to defining a biker, if you like bikes, take pleasure (not quite in that way
) from riding them and enjoy chatting about them then you qualify, whether you've passed your test or not.