She was 23/24 when Happy Days
ended and just couldn't fit in beyond that. To give you some proper perspective, she (with all due respect) wasn't hot enough to be the ingenue. On the contrary, she wasn't fat enough for the quirky best friend. Also, she was too famous to be a character actress and she was still too young to be plausible as the mom. And at the end of the day. she wasn't good enough to transcend those issues. In the end, her bigger issues were likely that she had drug issues and she wasn't that a good actress to begin with.