If you were cosleeping until 3 months ago, you are expecting too much from her too quickly.
Also - if you are going to leave her to cry, she should be in a cot and not a bed. You will end up establishing very unhealthy sleep habits that means she can just be up and about as she pleases in the night, also she could well start falling asleep by the doorway or on the floor. She needs to be in a cot.
I would also stick out the crying with you in the room. Don't leave her alone, it wont solve any of your problems.
Yes, I know it will be stressful for you to be there while she cries for hours. It will be more stressful for her alone, remember that and suck it up.
In the room, with her in a cot - you need to establish the behaviour boundaries you expect. Start off with - you must lie down in your cot. Just that, nothing more. So at every time she gets up, tell her to lie back down. This (a) keeps her safe and not climbing the cot. And (b) gets her in a position to go to sleep.
She'll fight you with just having to stay lying down at first. So be it, have that battle. Be compassionate but firm. Once she's accepted that behaviour boundary and no longer pushes kit, next boundary is - You lie down and are quiet.
Again you/DH stay in there to establish the rules. She is pushing behaviour boundaries. You need to be firm with the behaviour you expect. You also must be consistant in your expectations, at all times. This includes bedtime and naptime.