Sensitive Child

Hai,
My daughter is 6year old. She satrted kindergarten this year.
She is very sensitive and emotional. She cries for each and everything. At school during lunch she says other kids tease her that her food is smelly & looks disgusting..yucky so she never eats her lunch. Sometimes other kids are very mean to her like the other day 3 of her friends had come to our house. One of the little girl was sitting next to me & talking to my daughter who was standing infront of me. The little girl farted & started saying to all the other kids that my daughter farted & she really made them belive that and they started teasing my daughter this made her very upset and she started crying. Other times they cut her out saying we don't want to play with you or don't want to tell youa secret. I really don't know how to react in these situations. My daughter has become very quite & dull these days. She cries a lot. It seems like she has lost her confidence due to all these teasings. Please help me