I would look online at like Stateline tack or something for a bit that would fit her, they do have smaller bits that are french link, and truthfully the horse is SUPPOSED to chew on the bit. If she's leaving teeth marks on it, then it is not sitting in her mouth right, it's either hanging to low, or is pulled too tight in her mouth, and needs to be adjusted accordingly. There are different types of chewing, the good is just simply chewing while still going along nicely, and the bad is anything from grinding the teeth, to gapping the mouth, to tweaking the head and holding the bit between the teeth to get away from the bit. I would not jump to putting her in a hackamore just because she is chewing on a bit, especially one that doesn't fit right. I don't know if you ride western or english, but either way, after getting a bit that fits her right, stabilize it in her mouth with a correct fitting flash, and see if that helps calm her chewing a bit. Good luck with her, and I hope that you are able to find a bit that fits. Again, look online, at stateline, or do a search and I'm sure that you will be able to find what you are looking for.