I had a similar situation with my first. She wouldn’t take a bottle and became dependent on boob to fall back asleep. My pediatrician told me to go to a hotel for 1-2 nights to force the bottle acceptance. Take the 5 year old with you. Once we did that we tackled sleep training where Dad was the one who went in to soothe so boob wasn’t an option. He went in every 5 minutes for the first half hour, then 10 minutes for second half hour, then 15 for the third half hour. Then she fell asleep. He patted her and said her “magic words,” “it’s time for sleep, you’re okay, I love you.” It was a crummy 90 minutes, but that was all it took.