<human>: Can you provide a brief overview of the text?

We started hooking up 2 months ago. I had/have been hung up on an ex & my FWB is a commitment-phobe; we've been open about this from day 1. We run in the same social circle but weren't close before we hooked up. Our interactions have progressed to have dating-like qualities -- meals, parties, date functions, falling asleep on the phone, etc. 

We've reached shit-or-get-off-the-pot time. I care about this girl but recently I've realized I'm definitively not interested in a relationship with her. I feel strongly about addressing it directly (vs fading out or dropping hints) but I am curious: How much explanation is appropriate to give her? FWIW, I do not expect her to be crushed by this conversation, however, I would not be surprised if she tries to negotiate keeping it FWB. I am firmly against that option for multiple reasons, some related to the inevitable progression of feelings on my and/or her end, more related to her habits/traits like dishonesty, extreme conflict avoidance, and lack of compassion. Essentially, what were minor nuisances starting off as FWB are complete dealbreakers for any ongoing intimate interactions.

Any tips on how/what to say? I had a great time and I care about her a lot. Frankly, I might be more upset that she's not a good relationship fit for me than vice versa. She's likely to play tough and act indifferent; she's unlikely to tell me if she has unanswered questions or if she wants to hear more or less from me. I won't say anything untrue and I won't leave her with any false hope of continuing. I'm open to giving her closure/explanations but have no idea where the line falls between honest and hurtful.
<bot>: FWB for 2 months. Started to feel like we're dating but I'm not interested in a relationship with her. Seeking guidance on how much/what to say when I end this.