This is from the educational serial Extra English s01 (Hector’s Arrival). Here's a part of the script.
BRIDGET [reading email message] ‘Gigi!! Did you get my message? Please call me. Love, John. P.S: Did you get the flowers?’
BRIDGET Is he stupid?! (Writes email) ‘I told you last night, it’s finished. Sorry. B. (And don’t call me GIGI.)’
What is this contraction for - it's finished - it is or it was? (in this context).