My eldest was just like that. Always had to rock her to sleep and could only put her down when she was fast enough on to not wake when I did. When she was about two and my second was on the way I got some advice on controlled crying. The idea was for her to learn to go to sleep on her own, so I'd settle her down, then leave the room. If she started crying, give it 5 minutes, then head back in to settle her, but not pick her up this time. Repeat, leaving it a little longer each time. It was so hard and I had to try and get out of earshot, because I couldn't bear to hear her crying.

This gives some good ideas that may be helpful: https://www.mumsnet.com/babies/sleep-training-and-controlled-crying