Tis' the changes of a child. She is probably going through developmental changes or about to hit new milestones. This is what typically happens. It's normal. It's a phase. One phase of many. At 2 years old it happens again.
Sleep is not static in a child. But you are lucky your little one has been a good sleeper.
Just keep consistent in your nap/bedtime routines and times. This is important. It will pass.
When they go through these changes, it's not easy for them either. So, just be patient.
She could also be going through teething, or "night terrors" (look it up online) and these are normal too. It's developmental.
She could also be hungry, as she is growing.
Or, she may be getting sick or not feeling well... this is also how they behave when they don't feel well.
Or, it could be "separation anxiety", and yes, it's normal at this age, and even when they are in their crib and "supposed" to be sleeping... their "emotions" are ALSO developing... and this is a new thing for them.
It is many things at the same time, that a baby or child has to adjust too. They are changing so fast each month.
The Toddler years from about 2 years old will bring another set of sleep issues... for the Parent. So head's up. EACH age has different manifestations of sleep changes and emotions. Such is the life for a child, and then the Parent.
A great book series is "Your 1 year old" or "Your 2 year old." You can find it on www.amazon.com It has a book for each age of a child. Its a fast easy read and explains each age and what they go through. It's great to understand them, from a child's perspective.
All the best, I know it's tiring.. but they grow up so fast. Lack of sleep for parents is the thing we can't always avoid. One day you will miss it. :)
take care,
Susan