I listened to both Walk On By and I Can't Make You Love Me. The mix was decent. I DO NOT agree about the vocals needing any adjustment in the mix. They sit well, are very smooth, and articulate. I don't hear the midrange problems described at all. Do share what mic and preamp you used. I did detect just a bit of mud in I Can't Make You Love Me mainly during the transitions.
I think the piano could use a little space around it. It is very dry. In the intro, it is OBVIOUSLY a synth module piano sound. Don't dig that too much......
I think the comment about the bass is somewhat on the mark. I was thinking more that it needs a little more presence. Maybe a hair of boost around 300Hz. A bit more compression. Although, the compression and eq idea may not work so well as this soundsl like a soundfont or synth module, and usually those kinds of sounds don't lend themselves to eq/compression so well....

I am no fan of the whole soundfont/synth module thing. Drum machines either.
But all in all, not a bad mix.
From a producers stand point. The singer really needs to work her upper and lower ranges before she is ready for the next step up. She doesn't sound comfortable when she goes low, and the higher notes seem to be a little too "cut loose". I also hear a few diction problems. Some of the ways she is pronouncing words makes them sound sort of weird. I wouldn't even share this if I didn't think she had some potential. I sounds like she is nearing the point where she is stretching her talent. Generally, for this kind of music, that is not such a good thing. Command is what this all about! Command comes from preforming what is well below the extent of your talent.
Autotune on the voice? I detect a bit of the hash it can create, but I don't hear it totally abused either. Hard to tell from a mp3. Oh, and the encoder you used would seem to be pretty decent. Stick with it...
Ed