Difficult eater

My daughter is 8 months old . She has been using Avent bottles since birth. She eats anywhere from 4-8oz a feeding usually . But recently she will start fighting the bottle like she isn’t hungry . It could be 5+ hours and she won’t eat . Or she’ll act like she wants it but then suck for a little bit and then spit it out. I increased the nipple size and it worked for a bit but even sometimes she’ll act like it’s too fast but with the lower one she gets frustrated often . I don’t know if it’s the bottle type, or that she just isn’t hungry or maybe teething . Does anybody have any insight to this? I’d appreciate any tips/info . Thank you!