Why the confusion?
After getting dressed we were in a hurry to go out from the house, but the younger sister was drinking her milk. So I did not want to rush her. Otherwise she would have stopped drinking her milk"
I'd change it to:
After getting dressed we were in a hurry to go out of the house, but the younger sister was drinking her milk. I did not want to rush her, lest she stopped drinking her milk"
Thank you for your reply. If I use "she would have stopped drinking her milk" is it grammatically wrong?