Confidence....Humor....and just be yourself. If you are not comfortable with who you are, people can't be comfortable either. Chances are she might be just as insecure about the same things. Remember....a good relationship must always have TWO things: HONESTY and TRUST...You can't trust someone who's not honest...and you can't respect someone you can't trust.
If you and your girlfriend are on the lease or rental agreement, then I do not think they can. You would have to talk to the property manager or landlord. If neither of you have any paperwork to the contrary and there is no paper trail....you may be SOL.