Best formula &/or bottles for baby uninterested in eating?

Before I start getting “breast is best” responses, I can’t breastfeed due to my own medical problems. My lil girl just spent 14 days in 2 different hospitals for “feeding problems” that was eventually attributed to “coordination and developmental issues”. She was discharged with a NG tube which breaks my heart. She’s currently using Dr. Brown’s bottles with a Preemie nipple and Similac Sensitive (she was not premature). IMPO, she gets frustrated with the extra slow flow of the nipple and gives up and she isn’t a fan of the Similac Sensitive. Has anyone else been through a similar situation? What eventually worked for you (please don’t say “just give it time and it’ll suddenly click”)?