Hello, Welcome to HCM, I am Dr. Das
Firstly, your girl friend is most probably suffering from hypothyroidism
It is not an infective disease and it is not transmitted by intercourse or sexual activity.
So, there is no chance of getting any infection due to thyroid disorder
If, your partner has any sexually transmitted disease
, then only you have chances to get infected.
But the symptoms you told indicates presence of a sore throat
, for this you have to consult with any general physician for further management.