Toddler with an underbite

My 2.5 year old has an underbite. I noticed it when she was a baby, not a big deal. when my daughter's teeth first started coming in she had an issue with grinding. Still grinds them on occasion, but I've kept her on a bottle for that purpose. I would rather her chew on the nipple then grind her teeth. She also drinks out of sippy cups and stuff but not very well yet. She's never taken a pacifier, she was breastfed for 4 months and had no problem going onto a bottle. Now that my child is eating food, it's turning out to be a big deal. She doesn't take big bites out of stuff, she chews with her mouth closed. Perfect child right? She's chewing with her mouth closed because she's trying to chew with an underbite. And brought her to the dentist back in February because I was concerned about the grinding. It wasn't a good experience. They had no idea how to treat a child and had a lot of nerve offering dental services to children. So we haven't been back and I plan on taking her somewhere else in the near future, like very near lol. Has anyone else had any problems with baby underbites and eating? Any advice?