I agree with the poster below.
It's not creepy if it's kept professional and within the context of the site.
P.S. If a woman is offended or weirded out by a man friending her, I would imagine that her response to that would be to simply defriend you. No biggie. As long as you weren't inappropriate, so what?
Your wife is right, you're over-thinking it. However, it was a great question to ask.