The term “not finished” means that she probably doesn’t have a lot of experience under saddle.  I’ve found that inexperienced horse + inexperienced rider = disaster.  If you have some experience and the horse is fairly calm then you might be OK.  Honestly, you can’t go wrong with at least trying it out because they have a 30 day satisfaction guarantee and they will send you your money back.  Just make sure the first time you try it on her you are in an arena or round pen where the horse can’t any real speed up on you.  I tried the Dr.Cook’s Bitless Bridle with my young horse and he did great with it.  The first thing he wanted to do was push his nose out and throw his head up.  A gentle sawing back and forth on the reins got his head back where it belongs.  While cantering he got a little excited and again, I used the sawing back and forth motion to get his attention (this time with authority – not so gentle) and he did very well.  I did end up sending the bridle back but not because I didn’t like it…because my horse is very hyper and I just had to use more muscle than I wanted to control him.

Good luck.