I wouldn't recommend 10 inches to any rookie, especially a young one. Start out with a moderately thick 7 or 8 inch bull. If a woman is used to getting fucked by a cigarette sized cock getting a big one stuffed into her may not be a pleasant experience if the bull doesn't exhibit some patience. The most pussies will stretch to accommodate nearly any cock, but there are women out there that just can't handle a really big one. A lot has to do with attitude. Does she really want it, or do you really want her to have it? It makes a difference. Regardless of how things go it will change your relationship.