I wouldn't use the word "cheating," but she is behaving in a way that says loud and clear that she's not your partner in a loving, long-term, mutually beneficial relationship (LLTMBR). The behavior I'm talking about is that she discusses your relationship challenges with a guy she's known for a month who is openly courting her.
In other words, she exposes your vulnerability to a predator. (or maybe I should say "rival."
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That's not what LLTMBR partners do to each other. She's just not available for an LLTMBR. That doesn't make her wrong, and it doesn't make it cheating; it is simply feedback for you. You get to choose whether or not you want to work at being in a relationship with someone who is not available. There is a lot of growth available to you in going through that pain! It's not the avenue for growth that I would choose (I prefer to feel good), but it could be valuable for you to plug on, thinking she's your partner.
Or, you could generously let her go with love, and free her and yourself to find a relationship that will work well for each of you. You could let go of thinking that this is a partnership you're in, and just have fun with her when she's around, and immediately start dating other women, at least three of them.
The interesting thing, I think, will be that just letting her know that you are generously granting her and yourself the freedom of not thinking of it as an LLTMBR, that you are no longer held by the bounds of monogamy despite your tremendous love for her, will give her the opportunity to have a growth experience of her own; it's not just for you.
So, how generous are you willing to be in this relationship?