Why did Louise Marwood quit Emmerdale as Chrissie White? Who does she play in Coronation Street?

Coronation Street spoilers tonight: Hope plots to ruin Fiz and Phill’s wedding day?

Coronation Street spoiler see Fiz's wedding surprise of two blasts from the past

What is wrong with Nicola in Emmerdale? Why was she attacked and is she suffering from PTSD?