B.M.
She's 19 months old, when she wakes up she needs adult supervision. So when she gets up, go get her and get her out of the room so her sister can sleep. You can bring her to your room for some extra cuddle/snooze time, or you can start the day but she shouldnt be left to her own devices. I think its unrealistic to expect a 19 month old to get up and play quietly while the rest of the family sleeps. Yeah, it sucks when you have a kid who thinks they're a rooster-my daughter has always been an early riser and 7:30 is *late* for her and only happens once a month, but thats part of being a parent and you grin and bear it and know that one day you might sleep again.