At 8 months I would not worry but I know can be frustrating as my DD is 13.5 months and not crawling and only just commando crawling. I want a moving baby like all her little friends, so we can enjoy play centres and parks more. The past week she has shown signs of cruising and can go from sitting to tummy so she is getting there. She loved tummy time but has never rolled. Apparently she is very verbal so might be making up for lack of mobility in that regard. We do crawling exercises here and I crawl around and point at other babies crawling to encourage her but she is a fair bit older than your DD and not crawling at 12 months is less "normal". I have never googled so have not worried from that aspect, just resigned myself to fact she will do in her own time.