V.B.
I think she's fine. My son took forever to talk (he probably only had a couple of words at your daughter's age), but he is 27 months now and he talks up a storm and most people can understand him now. His speech has changed so much, even in just the past month, it's incredible. He also walked at 9 months old, so his doctor told me to be prepared that he would likely start talking later. I would say if she isn't talking much better by around 2 1/2, then I would have her evaluated, but she isn't even 2 yet, I would give her some more time. It's hard not to compare your kids. My daughter (older sister) was also talking in complete sentences and understood by everyone at 17 months old, so it was tough to wait it out for my son to "keep up", but they are such different kids that comparing them is just nonsense. My vote is that she'll get there with more time!
As the youngest, part of the issue could be that people talk for her (older siblings are notorious for that), so be sure that you are making her ask for what she wants and repeat it back to her so that she can hear you say the words too. This may help her articulate better. Good luck!