D.M.
This is tough. I think at this age they often develop fears of the dark etc... and really just need you. My daughter did this. I would try to understand what she needed - you can try a night light, blanket etc. Eventually she was in a big girl bed, and I still (at 4) put her to bed and stay until she goes to sleep. I know -breaking all the rules, but she and I have that time to bond, and it's become our routine. She still will get up in the night to find me, but I figure she needs the comfort and so I enjoy that time as much as I can . Someday she won't want me there anymore. Just know that there is no right answer - just what works for you and her - good luck!