Laverne and Shirley was a Garry Marshall production. Marshall was big on having a small "family" in his shows. Cindy Williams had a falling out with Penny Marshall, who was Gary Marshall's sister. She got cut out of the series and that pretty much killed her career.
She was cute rather than hot, didn't age well, and was an okay comedic actress, but nothing special, so her exit from Laverne and Shirley was pretty much it.
American Graffiti was popular, but it never got the recognition it deserved. It was a major influence in storytelling and editing.
One of the reasons Cindy Williams left the show was because she was pregnant.
She married an Army medic (on the show), they taped the wedding in a hospital ward set, where her fiancé was wrapped up from head to toe in gauze, like an Egyptian mummy. He supposedly had a rash. The viewers never heard him speak. It was a ridiculous story line.
Then, for a number of episodes, they showed a very pregnant Shirley (Cindy).
Then Shirley went off to join her Army medic husband on a military base, and from that point on, it was the “Laverne and Company” Show, minus Shirley. Kinda jumped the shark at that point.
I didn’t know about Penny and Cindy having a falling out.