N.B.
Too late!! You've already started that "bad habit"!! STOP! Leave her alone. you don't think she's hungry or thirsty, wet diapers don't need to be changed in the night (don't start another bad habit), so it must be just a normal fluctuation in her sleep cycle. Kids go through them every few months. (She may be having night terrors, though she's a little young for those. Kids usually wake up screaming from them.) In any case, DON'T remove her from her bed. Lay her down if she's standing up, pat her, and don't say anything more than shushhh til she calms down and relaxes. Walk away, if she starts up, walk back, pat some more, shush some more, and walk away again. She'll get the idea that nothing else is gonna happen, and she'll give up and go back to sleep. It may take a few nights to break the cycle, but it will work if you don't give in and take her out of bed.