We had a similar problem when our DD turned 11 months, she slept well up to that point, always had to cuddle her to sleep then transfer her in and she would normally have just one wake up a night, so we'd feed, cuddle, sleep, easy.
Fast forward to 11 months and all hell broke loose for no apparent reason, she started waking up as soon as putting her down, or 45mins later, or 2 hours later, basically she was up and down like a yoyo and taking longer and longer to cuddle to sleep, and it was always me she wanted, not DH, I work around my partners shifts and often don't go to bed till 2am, so was getting about 3 hours sleep a night and dead on my feet, heading for breakdown.
One evening my sister popped round, DD woke up and she offered to go up to her, obviously she was still crying 5 mins later so I went up, then as soon as I picked her up off sis she immediately stopped crying, no tears or shuddering, just stopped like turning off a tap.. I knew then that she was just doing it to get me to go to her and she wasn't actually upset.. and something in my mind changed, in that moment I understood her need for wanting to be with me, but also understood that my need to sleep and function was now more important than that, so the next night I decided to sleep train via CIO, I researched and I new ferber would confuse her, so I did the exact same routine but instead of sitting in the chair cuddling I put her in bed and kissed her good night and left her. She cried for 15 minutes at the bars, then lay down and went to sleep for 12 hours straight, I couldn't believe it, it went on like that for a week, day 4 was the worst, about 35 mins, but apparently they go 'all in' before they finally give up, but after a week, she was going to bed with a smile, and sleeping through every night till at least 7am.. it was BLISS, and she was happy! she was happier/less niggly in the day as she was more rested.
The only thing you have to watch is your last wake window.. you have to make sure it's sufficiently long enough so you're not trying to get them to sleep when they're not tired enough, otherwise it's unfair on them I think, we always adjusted her bedtime to match her optimum wake window after that and she dropped all naps before she was two anyway so was always ready for bed.
A lot of people think CIO is cruel, and I was one of them, but to be honest our DD cried collectively more throughout the night at various points, before the sleep training then she ever did during. Obviously not all children respond the same, and you have to hold your nerve, but I don't regret it for a second. It was a literal game changer for us.