It is much harder to sleep train a baby once they are over 14 months. It will take weeks rather than days. This post might help: https://www.instagram.com/p/DGxK_m5oTyN/?img_index=6&igsh=YWxmYWV2ZmNxN3Nk
Can you do something between the two methods for a bit and gradually reduce? I.e. cuddle for a bit until almost asleep and then put into her cot. You may need to stroke her back/bum or just rest hand on her back or in place for a bit when you put her down, until she falls asleep there. Then maybe you can gradually put her down more half asleep and/or not wait with her until she falls asleep. My lo had always self settled, but did have a bug plus all her molars coming through a couple of months ago, where I cuddled her to sleep for a week, and thought I was going to be stuck with that. But she returned to self settling after a bit of doing the above. Does yours go to nursery, or other childcare? Do they still go down for naps ok there if so? You may find getting someone else to do bedtime routine helps too.
I'd try a gentler method. My daughter used to self settle really well, we'd pop her in her cot and she'd drift off. When she was about 11 months, she started really screaming and crying when we left her room. We started lying beside her cot while she went to sleep. The first night she thought it was a game and she kept looking out through the bars of the cot, second night she was asleep after 10 minutes. Our plan was to gradually stop doing this but we had other spanners in the works with multiple colds and travel. We still lie with her while she falls asleep but we like it now. There are other gentle sleep training methods you could try if you want something more structured. Lucy Wolfe is a good one.