9 month old sitting up issues?

Rachael

Hey guys my baby girls now 9 months old she’s my fourth baby. By 6 months my other 3 we’re sitting unsupported now, she sits up but after a little while she will flop back and not want to know. So at the moment I’m on edge leaving her to it because of her doing this. I sit by her n have toys in front of her or sit her in her ring or ball pool but darent leave her unattended because we have wooden flooring. Is this ok for her to be this way? The health visitor said she will see if she needs physio but I don’t think she will because she’s very strong she walks back and forth in her walker and rolls both ways n pulls herself up n stuff