The family were a bit taken back by Jennifer's decision but were fine about it and just went on being their usual embarrassing selves. Frank asking her what she wore under her dress ( forgetting they don't wear habits anymore) Marie baking a cake in the form of a crucifix. Debra was the one to be really upset because she'd hope that Jennifer would be around for her more often. They treated her much better than they did Lois and Warren.
SkiesAreBlue

I haven't seen the episode in a while, but I thought I remembered Robert being just as uncomfortable around her as the rest of the family (except Marie) when she announced she was becoming a nun

She and Robert seemed to hit if off. They had a good rapport with each other which was refreshing as Robert is so weird around Lois. She was this wild child in the past with Debra being the "straight" one and I loved it when she was reminiscing with Robert.
SkiesAreBlue

She was awful! She had a weird, cold, wooden way of delivering her lines and had no chemistry whatsoever with the other actors.

Because she was incompatible with all the other characters, that's why. There would have been absolutely nothing for her to say or do that would have made any sense. So she was essentially Chuck Cunninghammed off the show. Just like Uncle Max in the comic strip Calvin & Hobbes, where creator Bill Watterson expressed regret over introducing the character in the first place. Makes sense to me!