Yael was after Mattan Torah. Yehuda was not Oiver an Aveira. The Medrash says that Yehuda started walking past her when his Taava started yelling, “Yehuda, what will be with Malchus Beis David!?” I don’t know if he ever knew it, but he was forced into it.
You can also learn Pshat like the Or Hachaim Hakadosh in Ki Seitzei that when a person who erradicated lowly desires suddenly feels drawn to something, he knows there must be something to it.
Old Man,
I think that the phrase was used but not in a litteral sense. Nobody was Mechallel Shabbos to greet a Malach. But, perhaps somebody took a small break from learning for the long term benefit.
With a Baal Teshuva, some utilize the concept of Mutav Sheyechalelu Shabbos Echad Velo Yechallelu Shabbasos Harbe, rather we should desecrate one Shabbos than desecrating many. Rav Illowey, a famous rav in America and a Talmid of the Chasam Sofer, allowed a woman to travel by train on Shabbos to come to Shul. He knew that it is her lifeline to Yiddishkeit and there is no real Issur involved, or there are many applicable Hetteirim.