I see what your saying now, apologies for the misunderstanding and thel accusation.
As far as EQ's go, I love FabFilter Q–but that's me personally. Any EQ will work, I would recommend buying one the has a built in spectrum analyzer. I know that FabFilter offers a fully functioning 30-day demo...
If you want to layer the vocals together to create a nice thick harmony (which is a great approach), you will need atleast three total versions. If your singer is willing, have her do three takes:
Take 1: The main vocal performed within the desired pitch range/key (we'll call this the original.
Take 2: The main vocal performed at a higher pitch than the original, but with minimum vocal range variation (a more "monotone" timbre).
Take 3. The main vocal performed at a lower pitch than the original, but with minimum vocal range variation (again, a "monotone" timbre).
When it comes to combining them, there's lots of different approaches. For example, after placing each take on separate mono tracks, you can setup the channel outputs like so:
Take 1 Channel Output assigned to a buss named "All Vox."
Take 2 and Take 3 Channel Outputs assigned to a buss named "Background Vox."
Change the Buss Output of "Background Vox" to "All Vox."
Now you can add some chorus or other stereo driven FX to your "Background Vox" buss without affecting the main vocal (Take 1).
This is just one very condensed approach. I've seen some tutorials where the background vocal is sent to two channels with each channel panned hard left/right, respectively, to add dramatic width. Again, experiment a bit. As long as you have the multiple takes, you're good to go.
Cheers.