My 7mth old

I try not to compare my LO to other people's babies around the same age cuz I know it will drive me crazy and every baby if different. I didn't think anything of my daughter not sitting up unassisted cuz she's already crawling and shows no interest of really wanting to sit. She's a mover not a sitter and She's pulling her self up on stuff. Well she had an appointment today for her reflux and the doctor said if she's not sitting on her own by 8mths then they will have to look into her being delayed. She says mama dada papa baba. I never thought cuz she don't care to sit that would be considered a delay. Anyone else going thru this?