Pretty has nothing to do with it. What is pretty to one guy might be disgusting to another and what ugly to someone could be beautiful to another. Girls can almost ALWAYS have another option it's just about if they go for it or not.
I consider myself pretty and i have definitely had that regret before . "Pretty girls" like guys too . Every guy that comes along a "pretty girls" path is not necessarily there" type" or can compare to the one they missed out on .