Not you're not. Whether it's green primer, or green concealer, you have to apply another product to cover the green.
Let me explain, first you apply the green, until you don't see the red anymore, then you apply another product (something matching your skintone) to hide the green. Then set.
I use a green primer (the HD from Makeup Forever), which will leave a certain green sheen to my face if i only apply it, but it's made to cover redness only. That's why once it's dry i apply my liquid foundation above, and set.
I personally prefer to use a green primer. Once you applied your foundation, you don't see the green anymore. The green concealer is really tricky to blend and cover, it's something i haven't mastered yet.
I suggest a medium coverage foundation, which you would layer and pat on. This ensures a better coverage on the areas needed.
Because i think it's also an inflammation/irritation of the skin (in my case), i also tend to use my mineral foundation, which i find more soothing.
Another thing your mother could look into is camouflage makeup, which is designed also to cover rosacea. I hear Dermablend from Vichy is quite good. Some theatrical products might also help, i was thinking of tattoo cover from Ben Nye.