Awww guys! Thanks! I still don't know everything though, I just love my snails!
Unless she detaches from her shell from an injury, she won't lose her shell.
The shells grow like fingernails. Like Stroke said, the cuttle bone (bird stuff) will help to make the shell nice, since it's calcium. I add about 1/4 tsp-1 tsp in my tanks about every 2 weeks, ground up with a cheese grater. You could probably go with just 1/4 tsp if you only have the one snail. I have a pantload of snails, so I use a little more.