Many greyhounds (maybe all kinds of dogs, I don't have much other breed experience) don't like strange dogs getting in their face. Butt sniffs, fine, face time, not so much! I know the other dogs were just looking at her, but if she was feeling insecure, that could be enough. Give her time and respect what she feels uncomfortable with. She'll relax, but may not be a good m&g dog.
I love Heather's (KennelMom) description of m&gs from the dogs point of view