My therapist said it's ok to be angry, but it's how I take it out is what I need to learn.
I would agree with that. Bottling it up will likely mean it will surface at some point, and could be intense.
How many days do you think I should keep space between us before I contact her?
I have no idea. I would think you should base that on how you are feeling. Give yourself enough time to cool down.
You cannot control what she is doing, only how you react to it. You have every right to feel uncomfortable with this friendship (it could likely be an emotional affair) within the boundaries of your marriage, but in the end she will decide whether to end it and you will decide what to do from there.