It would be great if you two could have a Friends With Hairjob Benefits arrangement, but I agree with Snarknation that she needs something more from you than cumditioner. Very few women will turn down pussy licking if you're any good at it.

Beyond the mechanics of the arrangement, you need to talk to her, no matter how difficult that is. Be honest with her about where you see the relationship going (or not going) so she doesn't get her heart broken. Tell her how much her friendship means to you, but be clear that you don't see a long-term romantic relationship there. Hopefully she will accept this and you two can be FWHB, but don't be surprised if she wants more, or if she's hurt that you don't want more.

You might be on the verge of a very good thing, but you might also be about to lose a friend.

I wish you good luck! Let us know what happens.