According to the vet, she somehow took pesticides and that made her sick... My dad convinced that she was gone for a while during the walk in the morning and it was adjacent to the local pear orchard. Needless to say, he was told not to let her go ever again, by my grandma, who cried all night on the day Lucky got sick. I couldn't hold my tears either, not only because Lucky looked so painful but also because I knew how much my grandma loved Lucky. Next day, she came in to the dining room and said, "Is she dead...?", and I was very happy to answer, "No, Oba-chan, she is okay, we took her to the vet last night."
Lucky is such an adorable dog. She has gotten a lot better by now, and of course, my grandma looks happier than ever.