I was always told not to go to bed angry but to sort things out first, have a talk to your roomy and get it of your chest or it could fester away at you, let her know that you know what she has done but do it in a calm quiet manner, let her know you are dissapointed in her actions, it is easy to forgive but much harder to forget, unless you talk it out with her it will fester and one day explode, if she is a good friend it is worth the effort, if not it will still be worth the effort for your own piece of mind