Kicking/waking up

We had our LO in a lounger to sleep for the first 2 months. It worked beautifully until she grew out of it and we wanted her in the crib. 😭 We realize now that wasn’t the best idea. Anyway, she’s 4mo now and when her legs slowly drop, it wakes her up. We’re experimenting with best ways to put her down. She has a boob-sleep association—that’s a whole other issue.

We tried a sleep sack to stop her legs from falling so suddenly but then I reconsidered and figured it may be best to just let her get used to the legs falling to help her long term. Do you have any advice? Do we just need to just let her get used to the sensation?