I agree with most of what was said here, and even more, I suspect that she just wanted to find something to pin the blame on you for the breakdown of the relationship. People do that.
That said, I will note that sometimes people really are bad kissers. The thing that makes them bad kissers is that they're "one-sided" kissers -- they kiss without taking any feedback from the kissee into consideration! I know a few people who kiss me (squeeze me, finger me, grope me) like they're doing it to a brick. I'm not a brick! I'm a human being. And if someone kisses me really hard, bending my neck back, bruising my lips, and it hurts, I'm going to react that way (although I will probably try to do so as kindly as possible).
Most people, when they kiss or make love, approach it progressively -- they do a bit and see what reaction they get, then do a bit more. But others just slam it on, the harder the better, as though that somehow makes it more intense and therefore more pleasurable. I've even known guys who, when I'm catching my breath and grunting due to the discomfort say, "yeah, baby, you love it, doncha!" ??? Can they really be so out of sync??
If you want to be a good kisser, be attuned to your partner's response. If she's stiffening up, backing away, exerting muscle pressure to hold you at bay, or wiping off her face a lot, then maybe you need to change gears. But if she's relaxing, leaning into you, kissing you back and pressing every part of her body against you, then she's liking it!
Good luck and practice, Practice, PRACTICE!!
..c..