Should you know the "really good friend" ?

I have been with my boyfriend for about a year now. Recently I have become aware of a really good friend. I have met this person once. (We met her around the same time) She has been absent the past year for hang outs as well as a goodbye party, and a birthday party. If she is a really good friend doesn’t it make sence for her to have been around for the past year? Unfortunately my gut tells me something isn’t right. And was it wrong of me to ask to see the text that has been sent between the two of them?