How do you know for fact its mono? And not the flu or sinus', etc? If in fact you are infected with the Epstein Barr Virus , yes your girlfriend will come in contact with the highly contagious virus unless she could be just a carrier. Especially if her immune system is low or if she is under stress so on so forth.

,,, been there done that,,, mono for 2 yrs and they say it never leaves your system.