what sort of attractions are within a mile of the ship pier?
Well there's Carlos-n-Charlie's, I've never it made it past there.
Just kidding, there's a TON of little shops/restaurants/bars right along the ocean at the pier. You can wonder a few blocks inland, but I'd be careful after that. Also, Chankanaab Park is very nice and it's about a 10 minute cab ride. The fares are posted by the taxis, I think Chankanaab is $14pp now. I'd normally say no need for ANY excursion in Cozumel, but bein a young woman traveling alone, different rules apply and I'm sure you know how to watch out for yourself.