That's not the kind of thing I like to "rumor" about. Since Grace has never said, it would all be speculation.
Grace's exit from the show seems to not have been caused by that event she relates, even though from her perspective the two must seem connected. Internal memos from well before the event indicate there were concerns about how much she was costing (she had a contract) vs. how little they were using the character, and that they should not pick up her as a contract player after that her contract expired, but consider using her as a day player a la Nichelle. Why that didn't happen I don't know, but within two months of her final episode Roddenberry issued a memo suggesting bringing her back now and then.