HI C.,
You are a special gift to your daughter. You and her daddy are the only existence in the world for her to receive comfort and guidance. You are how she will view the world. Every single choice you make is her world. Testing you at 15 months, I don't think so. She is trying to tell you something. You are right to question what is going on, that is dead on. Now, step back and listen to your instincts, listen to your heart. Don't listen to that noise in your head of what the pediatrician says. Leave no assumption in place. Work as a team and brainstorm with your husband, let him try for a few nights so you can get yourself together and think - it is very hard when you are frustrated (trust me, I totally understand!).
For example, children that are healthy may have difficulty falling asleep, but with a simple, consistent routine, they fall asleep........but then they stay asleep (they could care less about "testing" their parents. If either one of these does not hold, you need to look to her health. Digestive disorders begin a little at a time, but 15 months is a very key period that I hear often. If she is fully vaccinated, espcially if you have given her thimerisol flu vaccines, you may be seeing the issues many other parents are seeing. There is not one single study that shows how children's bodies respond to the number of vaccines in our schedule. These reactions can be addressed, but now is the time. www.generationrescue.org and www.taca.org are great sights to learn about reversing vaccine damage. Remove the milk from her diet replacing with RiceDream or Almond milk first, that may dramatically alter her sleep capacities. Adding proibotics and cod liver oil will also aid digestion and reduce possible reflux.
Also, be sure she can breathe. None of us sleep laying down when we are congested. Hold her up or prop her after clearing her passages with saline spray.
With sincere hope for your daughters comfort, and your peace. J.