Originally Posted by my name is joe:
“i think it's being credited as co-written, not sure what that means exactly. I'm not imagining she's capable of writing music at this stage so presumably some or all of the lyrics are hers.”
It works like this: Writer credits often reflect commercial rather than artistic matters. It not unusual for a big performing artist to take a co-writing credit on the songs they release even if they had no hand in the writing. Why? The publishing royalties are worth much more than the performing royalties - especially if the song becomes successful and gets covered by other artists.
So, in return for having their song performed by a big name, a songwriter will often give up some of the rights by sharing the credit. They'll usually agree these things in advance before the song's even written. How much each person really contributes is pretty irrelevant - they care more about it being a big hit.
In Cher's case I'm guessing you're right - she may be contributing some lyrics. But either way she's getting co-writing credits because (hopefully) she's got smart people looking after her interests.