M.S.
When I was going through this transition with my 10 month old son there was a lot of crying (some mine, but mostly his). My mom said to me "They don't want to be in charge." Those words really changed my approach.
If she wakes up your other kids for a few days, it's OK. It's a vacation and they can sleep late the next day. They'll live. Just suck it up and have some really rotten nights. She'll scream and protest and break your heart, but she will go back to sleep on her own. Just check on her, lie her down tell you that you love her and leave the room. Repeat every few minutes. She will wear herself down and go to sleep. It may take an hour or more. But the next night it will take less time. Once she knows you're serious that this is the way it's going to be from now on, she'll be fine. But you've got to really commit to this. She'll be fine and won't remember after a week.
Check on her as often as you like. But if she (like my daughter) settles better on her own, then leave her to her own devices.
She is not a helpless baby at 14 months, she is a toddler who is learning how to manipulate you. I know it's hard when it's probably your last baby. It's tough love, but you are teaching her a valuable life skill, and it's really effective.
Maturity, like anything else worth having, does not come easily. Just remember, you're in charge.
Best of luck to you!