a promo pic of Shelley, 1978
Shelley left Charlie's Angels after only one season, and she was unfairly blamed for the ratings dip that season. But in reality, the series already experienced a huge dip in the ratings the season before she came in. It dropped from #4 in season 2 to #12 in season 3. By the 3rd season, the series was out of the top 10 shows of that year. And when season 4 came around, it seems the production put the burden of putting the show back into the top 10 on Shelley's shoulders. How? By limiting her lines and screen time as well recycling stories and under developing her character. It seems Shelley was fighting a losing battle. But in spite of all that, the series still landed at #18 (tied with CHiPs) in the ratings, in the top 20 shows that year.
a writeup about Shelley's leaving Charlie's Angels, 1980