Marriage requires commitment from both of you. If she is talking divorce and won't go to counseling, she may have already quit on you. If that's the case, there is precious little you can do but get a good attorney. In fact, since she keeps bringing it up, she may just be using the threat to beat you over the head.
My recommendation, having been through a divorce myself, would be to hire an attorney, have the divorce papers drawn up, then take them to her to sign. Tell her you love her and will do anything you can to save the marriage. You hope she will go to counseling with you, but if not, here's the divorce. You'll find out really quickly if she's serious about divorce or will change her mind about counseling to save the marriage. Either way, you'll know the truth. As much as it may hurt, it's better to know for sure.
If you are willing to work at the marriage, go to counseling, etc. to save it, but she is not willing to work, then the marriage will fail. One spouse working on the marriage will never carry it alone.
Ditto that. If she is that unhappy about so many little annoyances and is unwilling to consider counselling then my guess is she already has, at the very least, her eyes on someone else. As Jeff Foxworthy says, "if she hasn't already saddled up another horse she has at least cut one from the herd." She may have been planning the divorce for awhile and is just building her case in her own mind, i.e. giving herself an excuse. It is my experience that when divorce happens one person is prepared while the other is totally blind-sided.