Regardless of what she says I would tell her that you understand how she feels but that you need some time to think about it.
The last time the D word came up (7/30) at my house, I told my H I understood how he felt, which made him even madder and he told me I did not. I would definitely not commit. Maybe saying I understand that you feel that way or I apprecaite that you feel that way would work.
I don't want to hijack the thread, but I do want to address what hopefulinga said. My wife said the same thing when I told her "I understand that you feel that..." Her response was that I didn't understand anything. You have to remember that you are dealing with people who are just as much caught up in the whirlwind of emotions that you are. They are not thinking straight, even if they have convinced themselves that they are. Last night I had a meeting with my pastor and he gave me some words of advice that I would like to share with you. Basically he said that the fact that the two of still fight is both good and bad. It is bad in the sense that it continues to drive a wedge between the two of you. However it is good because it means that there is still an emotional connection between the two of you. Unless your H is an extreme rageaholic (in which case you probably would be better off with a D) he is probably like most people and doesn't get angry with people that he doesn't feel an emotional connection too in some way.
I know that this may be hard to hear, and it is something that I still struggle to accept, but as long as there is anger and there is sadness, and there is unhappiness then there is still love. All of these negative emotions, while not good for your relationship, are indicators that he/she still has feelings for you. It is when they stop having any kind of reaction to you at all that you should worry. Your job (and mine) is not to change how they feel but to change how we deal with our spouse and improve ourselves. Make your 180s and stick to them. This time is about you and making you into the person YOU want to be.
M 39, W 34 M 15 S 14, S 12, S 9, D 7, D 6 Separated: 7/2/2012 Served: 7/10/2012 Divorced 11/5/2012