Can I parboil ravioli? I am making dinner for a friend that is sick.

Agree they can be parboiled.
Also, if your friend likes, stuffed pasta like ravioli, kreplach, pirogi can be fried with great taste and texture results.

There are lots of similar casseroles which are baked. You might look for those recipes. It seems like you could assemble in advance and bake at your friends house with fewer steps.

You are truly a great friend! Yes, you can definitely parboil the ravioli. Or you could make up the entire dish, perhaps setting aside any topping cheeses that typically get added at the last minute, and cook the whole dish maybe 80-90%. Write her instructions to add the final cheese(s) and pop into the microwave at maybe 40-50% to finish cooking slowly. You don't want to toughen the ravioli by microwaving with too much power.