I've got a little one, who had similar issues. The things we forget to think about are; has there been a change to her daily routine? A new experience that may have been unsettling? I didn't think about all those things when I was having issues with getting my son to sleep at night, and he'd just want to chat or play. My son's pedi recommended having time at night in his room where we read a book and had a little chat before I said, 'okay it's time for bedtime and Mommy will be here if you need me, but big boys need their sleep'...if he'd wake up, I'd kiss him and repeat the same exact thing.
His doctor told me that any small change in the daily schedule or event that may have caused a unsettling, may increase the need for reassurance that Mommy is there and always will be when you need her.
Even now, we still run into issues at night...if the nap was not long enough or if we try something new during the day, it can throw the whole thing off. Just be consistent with your approach, and you don't have to be stearn or mean, we're Mommy's our jobs are to love and comfort.
Good luck!