A.C.
Maybe her frenula (the little thingie under her tongue that holds her tongue down)is too short & she can't physically suck right. My nephew had a cleft palate that was so small & so far back in his mouth that they didn't catch it for his first few weeks. He had a funky bottle (don't remember the name but probably googling cleft palate bottle would bring it up) & that's the only way he was able to suck.