I Have Recently Started Dating A Woman(about A Month Ago)

I have recently started dating a woman(about a month ago) who I am absolutely head over heels for. We connect on an amazing level. Within our first week of dating we knew each other's friends, family, intimate past details...and among this learning process I discovered she had a male best friend. One whom, she told me openly, was in love with her. But they had been strictly platonic friends for three years she said. During the conversation she revealed that she had talked to him in the past about guys she had been dating at the time. About fights or disagreements she had with her boyfriends, and had taken them to him, and he had bashed them openly, calling them childish and she deserved better. And from what she told me, I couldn't agree more. However, would that not be considered almost....cheating? Confiding in another man, who you know wants you to be his wife, and mocking the man you are in a relationship with, with that man. Should I not be concerned that she will be doing this same thing while we are dating? She is having dinner with him at his house tonight as I ask this. Should that not bother me? Am I being too cautious? I'd like a professionals thoughts on the matter.