As early as 14 months children can start being demanding and changing their ways- we need to guide them back into the healthy habits they need to continue. Even though she is resisting her sleep it doesn't mean she doesn't need it as you know. You often need to re-train children in sleep and other things as well.
Check this out to see different things to think about- sleep environment... http://www.lullabyluna.com/2008/12/happy-new-year.html
Try putting her down at 7 and getting her up at 7 everyday- even if she isn't going to sleep- the consistency can re-train her. Do the same for her nap. Put her down at 1 and get her at 3:30/4 or whatever you deem appropriate.
A good line to use as you figure out the waters of discipline is "Try that again"- not only do you want her to know when a behavior is inappropriate by pre-deciding an appropriate consequence that you consistently stick to- you also want to have her learn what the appropriate behavior is... "Try it again" gives her the chance to practice.
Here is a blog that has a lot of good information on discipline and guiding your child- go back in the past entries and find her reviews on a whole bunch of books:
http://heartpondering.wordpress.com/
C., mother of 3, sleep consultant, sleep blog writer