Blimey that's a terrible reaction you don't OWN your children and grandchildren your job is to let them live their lives as they see fit and honour their decisions My son emigrated to NZ 20 years ago, has a lovely wife, two children and a brilliant life how could I not be happy for him, although like others have said you are devasted inside I only see them every few years ...my youngest daughter and family are in Europe and I see them a couple of times a year ... but again it's their decisions not mine
You have hopefully brought your daughter up to be confident to make her own mind up about where she wants to live. Sad but get over it save up and visit and be very very glad for their new life
Maybe your daughter 'will never forgive you' for trying so selfishly to stifle her she's not your prisoner