Yeah, she probably feels (why, I have no idea) that ALL of your passion should be directed at her and that the guitar has a peice of you to which she has no access. You were playing before you met? If so, then she knew going in how important this is to you. Does she have something that means as much to her? Do you support her in that? If so, remind her of that ... gently...cuz' you don't want to get her feathers ruffled any more than they are now.

As a divorced guy, I am in no real position to over relationship advice but I would say this, it's a good thing to compromise in a relationship when trouble arrives. It's NEVER a good thing to capitulate on something that makes you who you are. It's virtually impossible to get over the resentment that comes from that sort of thing.

Best advice of all; just talk about it.

Good luck.