If a pornstar started growing on me, I'd cut her off when she fully developed and have my way with her... But that's just me.
To answer the question seriously, Rebecca Linares has grown on me quite substantially. Also Shyla Styles. Both to me at first were just a nice looking girl. But after watching a few of their movies each, I've begun to find some cross referencing to actual girls I've met, and found them to be more "personal".
Almost forgot to add in the best MILF ever... Vicky Vette... First time I saw her I thought "meh she's hot, but is probably stuck up" and boy was I ever wrong! She's still hot of course, but she's so awesome to her fans. Wish I could do the same type of thing for her!