When one of my girls was 16 months she showed no interest in walking - she would stand up and then go nowhere. Like you we were starting to get a bit concerned. Then one day she just stood up , walked the length of the room, picked a toy off the shelf and walked back again! I called her over and she strolled over as if she'd been doing it for months - never crawled again.
As everybody's already said children do things when they are good and ready. As long as she seems he/she seems to be happy and healthy don't worry about it.
Oh, and ignore other mums telling you what their ' child prodigies' can do - there's always one that's walking, talking, juggling, writing computer programmes by the time they're a year old.LOL