I just went through this. We were worried her reaction would be anywhere on the spectrum from ok to pyscho.
Anyway we told my SD and then when my DH took her back to her mum's he said 'she has some news' so SD told her mum. Surprisingly she was happy for us.
I actually dropped my SD off to hers the other day and she was friendly and said congratulations and we talked for about 10 mins and she was telling me pregnancy stories and giving me tips... It was weird given her behavior to me in the past but I'll take it cos I'd her be friendly (even if it's fake) then be nasty to my face!!