Yours is a hard question to respond to without more information. Avoiding eye contact and conversation are not necessarily the same things. There is a technical term for not looking people in the eyes – gaze aversion – and it sometimes signals some level of emotional disturbance or a developmental delay. Not talking to teachers may be just shyness, but it could also mean that your daughter has somehow developed a high level of anxiety in her interactions with them. On the basis of what you write, I don't find proof that she's being stubborn.
You need to make a private appointment with her primary teacher. Be very observant of what the teacher says with both her words and her body language. Do you think she really cares about your daughter? Do you think she blames your daughter for her behavior? Does she hint that your daughter is behind the other children developmentally? Try not to make it sound as though you blame her for your daughter's atypical behavior. If you do she will become defensive and you won't learn a thing. Ask her for suggestions of ways you could help at home, and don't hesitate to offer her suggestions of how to connect with your daughter.
Finally, a simple suggestion, but one that might be the most helpful of all: talk to your daughter. Ask her casually why she doesn't talk to her teachers. Ask if she understands what the teachers say to her or what they mean. You may be astonished by the wisdom in her reply.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.