1. Give your character a dilemma.
That way things can keep going round in a circle, to illustrate said dilemma. Particularly if she's also indecisive. Like, she wants him but she knows she can't have him but she really does want him but she really can't have him but...
Indecisiveness in general is also good, since you can add things like "oh, I don't know, I think I'll have the cheesecake... no, the pumpkin pie. Oh, I don't know. I'm so terrible at decisions. Help me, oh my hero, to make the right choice." (You'll be glad to know nothing like that appears in my novel, but you get the point.)
2. Have your character know something else well, and quote from it frequently.
Maybe she's a Christian, and keeps using the Bible to make her arguments. Or maybe he's a West Wing fan, and borrows Aaron Sorkin's words frequently. (I resisted that particular temptation this time - in fact, it took me till page 133 to mention the West Wing at all, and that's because I wanted my character to wear a suit and backpack, and didn't feel like I could do that without a nod at Josh Lyman.)
3. Get your character to speak a foreign language from time to time.
That way, they have to saw everything twice: once in the language, and once in translation.
4. Use circumlocution.
If he says, "no", that's one word. If "he shakes his head no", that's five. If he "explains", that's one word. Have him "say by way of explanation" instead, and get yourself some extra.
5. Show, don't tell.
Yes - at last some sensible writing advice that holds even if you're not doing NaNoWriMo. What I mean here is this, though: instead of saying, "she was kissing him", make it last: "she was kissing him, kissing him, kissing him". If their arguments are going in a circle, show it by making your narration go in a circle too: "And so they were back. Not to Square One exactly, more like the "go" square on the Monopoly board, they went round and round and they kept ending up in the same places, and round and round, but each time was different as well as familiar". There's a sneak preview into mine.