Any ideas on my puppy's breed?

We got this lovely puppy from our local shelter, but don't really know what breed she is. We think she is 3-4 months old (her baby teeth have just started to fall out), and she is almost 20lbs. Her two sisters looked similar, but with totally different coloring. One was brown and white, and the other was black brown and white. Any ideas?

If that was her in your profile picture. Cant really she the photo well... and i dot know what Lbs are, lol. Types of dogs she could be:- black german shepherd- black australian kelpie- ponerainan - black belgian shepherda mixture of these breeds. you can go to the vets and get a a DNA test to see which breed/s she is, i heard its around $70-80.