Seamanarts- I like the piece a lot and the join between the human half and horse half works well with the POV
There are a few areas that need to be attended to on the horse that stand out, First the forward front hoof/lower leg looks good but the shape of the hoof on the other front leg is slightly misshapen. The horse's rear left leg also needs to show the change of angle from the knee/patella area to the hock.
On the chest of the horse there should be a bit more definition of the pectoral muscles ( where the bottom of the neck meets the chest plane)
The only other thing, that you may already be working on is to resolve the difference between the lighting of the horse (multiply lighting sources as in a show arena) verses the single light source on the woman.
Some of these things you may already be working on resolving.
As far as the spear it's butt end would probably disappear behind her but by changing the angle she is holding it and being able to see both ends might solve the ambiguity of it.
Look forward to seeing it finished :)