My 20 month old has had a few occasions where he has fallen asleep on his own, but for the most part, he needs to be rocked or snuggled to sleep. Luckily he'll go to sleep with his daddy or with me (and has even fallen asleep pretty easily for Grandma a few times), but we can't just lay him down and walk away. He's a good sleeper, but he definitely still needs help falling asleep, and sometimes that means 30-45 minutes of rocking and/or laying next to him in bed to get him to sleep. Most nights it's not too bad (he falls asleep in less than 15 minutes usually, and for his nap he's down in 5 minutes max), but sometimes it can get frustrating because he'll wake up if you put him down too soon and then you have to pick him up and rock him all over again. You're not alone! He also needed to be held for naps from 4 months-11 months, or else he wouldn't sleep more than 20 minutes at a time. So I held him for every nap, the entire nap, for 7 months straight. So comparatively, a few minutes of rocking each night is not so bad for me! :D
From what I've heard from friends with toddlers, each kid is different, but most kids will start to be able to fall asleep more on there own consistently around the age of 3. Some are lucky and have babies that fall asleep on there own, and some kids still need someone to help them fall asleep until they're much older. But it won't last forever. I would try to get your toddler to fall asleep for daddy, so you can get a break, but it's not bad that she needs you to hold her to calm down and fall asleep.