Baby doesn’t drink bottle

Hello moms, My baby is 2 month and a half. She has been drinking my milk from bottle since she was born. Just couple days ago, she only wanted to drink from my breast. However; she usually falls asleep while drinking from my breasts and the feeding session doesn’t last longer than 15 mins. I tried to feed her with bottle and she kept biting the nipple and not swallow the milk. I am afraid that she is not getting enough milk. What should I do in this case? Please help! Thanks.