Either move the plants if you can, because if you prune, the tips of the plant will brown and be unattractive. Or, plant your smaller palnts in front of the liriope. Good luck, and maybe in the future you can post these types of questions in the perennial forums, since liriope is not an ornamental grass and is classified under the Liliaceae family, not Poacea....good luck

We had a hard freeze. Our Var Aztec grass looks realy bad. Can we cut it back to get rid of the brown? If yes how far?

If your temps got below 10°F, your plants probably suffered root kill, and may not survive. Cut them back to the ground, and cross your fingers. If enough root mass survived, they'll come back.