Theoretically babies don't self-wean before they are at least one year old, mostly they go longer than 1.5 year, even up to 5 years of age if allowed :lol: .
However, when they are teething they may refuse breast, they are uncomfortable with a nipple. Also, some babies will ask for breast non-stop while teething to comfort themselves, it just depends on your baby. But, in your case, it sounds more like your baby started prefering a bottle to your breast because of the faster flow. It happens often that a baby will chose a bottle because she doesn't need to work so hard to get her milk as she has to while nursing from the breast. You mentioned that you moved her to the next stage nipple and that explains it all. She has no problem sucking from the bottle whereas getting milk from your breast is more effort for her.
It is up to you, you can still switch her back to breast, if you get back to a slower nipple on her bottles and keep offering breast more often.
If you plan to wean anyway, just go ahead and continue what you are doing and she will eventually wean herself.
Of course, I would like to encourage you to keep nursing, you can try to keep some of her feeds, at least. Let us know how it goes.
