Controlled crying

I need help, my baby is 9 months old in 4 days and has Never fallen asleep by herself in her cot. Always been on the sete, or in bed with me. (My own fault)

Recently i have been putting her in her cot when shes sleeping and within half hour/1 hour she’s waking up either sat up or on her front crying for me, not settling. So I bring her Into bed then put her back in her cot again when I think she’s in a deep enough sleep. I’m worried that one time I’m going to fall asleep with her and she’s going to be in our bed all the time.

my questions are, should I leave her cry? how long of the crying until you step in so they are not stressed Anymore? What if the crying goes on all night and clearly shes so worked up an anxious. I hate her crying, always have but she’s ruling The roost at the moment and me and my partner are trying for another. (Mad I know)

advice please:(