All I can say is that her answer makes me feel like I've spent too much time on this computer.
I'll throw a random number in there. If these are serious relationships and not casual dating numbers, 5. For me, too many makes me believe the other person isn't really into having a relationship, or is just really bad at reading other people. Too little (as in, none) seems a little scary, as it can mean socially sheltered or unable to trust people. These are all coming out of my bum as I haven't dealt with this experience, and again, my number is fairly arbitrary. It really depends on the person, their experiences, and how comfortable I can be with them (and especially with myself).