How to settle playgroup to school environment? Any tips?

Recently, I'm being transferred to the playgroup cl from K1 cl. And obviously it's a huge gap. I have difficulties to settle them down. I have this student aged 23 months old. And she just came back from M'sia. Apart from that, she usually get to see her parents only once a month.She used to stay with her grandma in M'sia. But recently, her parent decided to bring her back to S'pore and stay with them. So at school, she will cry the whole day and chanting mommy and mommy. I tried distracting her with toys, food but to no avail. She refused to drink milk. But eating with the others, she have no problem. This is my first time handling this difficult situation. Do you have any tips to settle this child? Help, her cries is haunting me at night. I can even remember every single word she say. HELPPP!