I have a friend who is a Catholic but she is a good friend and she also respects our religion and has also fasted in the month of Ramadan. Does Islam allow us to communicate with and be friendly with Christians or members of other religions?
Yes, you are allowed to. The Holy Prophet (s) used to draw up peace treaties with non-Muslims that respected mutual rights. When the Qur'an says 'do not take the Jews and Christans as your awliya'', it means 'do not make them guardians and managers for your affairs'. You can still communicate with them, and if they are your neighbours you actually must communicate with them in order to observe their rights.