She'll only sleep latched on
Have you tried replacing nipple with a dummy?
Ideally keep everything else the same initially. So feed to slerp sleep next to you, then once asleep unlatch and whip dummy in really quickly. A hand on baby's chest can help calm if this stirs baby. Likewise either holding dummy in for baby or holding under baby chin to keep mouth closes around dummy.
It won't be an immediate magic wand, but work towards them being able to feed to sleep, swap for dummy and then you roll away, leavibg baby in your bed but not snuggled up to you.
Once baby is used to sleeping independantly like that, she may tolerate being in the cot more often. The problem at the moment is that going from cuddles very close to you, with your heartbeat and warmth, being able to comfort suck - to being alone, in silence, nothing in mouth and "exposed" (for want of a better word - I mean not cuddled up tight). I can easily see that being a jump too far. Making the change more gradually is more likely to be tolerated.
As well as the dummy, other tools for independant sleeping are:
- white noise. It drowns out background noise and replicates womb noise
- swaddle. You're on the late side for introducing This, swaddles should be started being used before 3 months. But a swaddle dulls down the startle reflex and generally reduces stimulation. This means a swaddled baby is easier to transfer. The swaddle also recreates the tight feeling of being held.
You'll notice that the tools on independant sleeping mainly replicate and replace attachment parenting ideals of cosleeping.
- Nipple in mouth when cosleeping, dummy when independant sleeping.
- White noise or your heartbeat and breathing.
- Swaddle or being cuddled
So an answer to all of this may be to just accept cosleeping and not attempt to fight it. But if you decide independant sleeping in the cot is better for your family, there are easy ways you can ease baby into this without distress.