Wa'alaikum assalam! Nine months is still totally normal lah, jangan risau, beberapa anak saya kenal pun crawled later, some around 10-11 months. The fact that dia boleh terbalik dan berguling is a great sign dia kuat dan koordinasi okay, merangkak usually comes after. Try giving her more tummy time on the floor, maybe put her favourite toy just out of reach so she's motivated to move towards it, sometimes yang triggers them to figure out the crawling motion, macam our babies know what they want haha. Kalau dia still tak try by 12 months, boleh check dengan paediatrician just to be sure everything's progressing well, tapi honestly most babies crawl when they're ready.