7 and a half month old can't sit unaided

[RollingRedHills]

My 7 and a half month old can't sit unaided for any longer than a few seconds- I try to encourage her and she just toppled over. She is commando crawling and can easily cross a room and rolls easily in both directions but hadn't mastered sitting. Should I be following this up with someone?

Thank you everyone this is reassuring. I think because she is rolling and crawling it's probably ok and I'm being a bit over anxious.

My nephew
Didnt roll till about 7 months.
Didnt sit till 11 months
Didnt crawl till 13 months
And only started walking at 18/19 months
Only had solid food at 12 months old as he choked all the time, would choke on a beaker.
He had no words till he was about 19 months but now at 23 months old, he says loads, climbs, runs and does not stop.

Dr at the time said wait and see, and although he is still behind, he is coming on leaps and bounds.

Every child is different, talk to the dr / health visitor if you have any concerns

My daughter went from looking like she was nowhere near to sitting up one, to sitting up perfectly the next day! I wouldn't worry.