Your daughter sounds exactly like my son (who is now 4.5). He started walking at 9 months and didn't crawl until he was over 14 months. One day my brother-in-law was crawling around on the floor playing with him and he just started to follow. It was very awkward for him at first - he kind of looked like a dinosaur - but he was excited by his new skill and eventually got better at it.
We didn't really do a whole lot to encourage it, just playing on the floor with him and modeling it. We did try to develop his upper body strength by offering him our hands to let him try to pull himself up when he wanted to stand up instead of just propping him up.
He continued to lack in upper body strength, even after he learned how to crawl (since he still preferred walking), so we did lots of climbing on monkey bars as he grew and swinging on the trapeze rings on the swingset. We obviously had to help him out a lot at first, but as he got stronger he was able to hold on by himself for longer and longer (this was more when he was 2-3 years old). Now at 4.5 his strength has caught up and is perfectly normal.
We had lots of people who said, "if he doesn't crawl he'll never learn to read (or do math, etc)", and I can assure you that he is developing just fine in all areas. So try not to worry too much, and just look for opportunities during play to encourage her upper body strength.
And I have to add, I didn't realize how good I had it with a kid who could only be mobile when I set him up. My daughter started crawling (and climbing) at 9 months and it was much more difficult to keep her out of trouble! Good luck!