She may have an ear or throat infection. This is not related to your exposure. Does she have any sharp pain going down from the back of the ear or any sore throat or pain in the throat? Any pus in the throat? I suspect she has some type of upper respiratory infection she is fighting off.
mkh9
hi my girlfriend isn't sick and today a lymph node popped up again behind her ear. It is red and painful. I know you said it could be any infection. Should I be worried still
Well, lymph nodes pop up due to fighting off any infection. They can arise in various parts of the body depending on where they are found. Also, how large they are is important because if they are tiny they may be normal. Also, if they are hard versus spongy. The role of the lymph node is to filter out bacteria and viruses. So they swell when they produce white cells that fight off infection. You don't even have to feel unwell to be fighting something off. Usually 10mm are when they are enlarged or under the jaw/neck 10-15mm.
If they are really tiny it isn't really anything to worry about. If it is a really hard ball attached to the skin then you could have it checked out. They should be soft and not tender.
mkh9