Character vs. Tension

In my new series, Dark Passions, I was having some trouble with my latest installment, The Vampire's Embrace. I had an idea for some lovely tension- a forced marriage, but the character that was supposed to get married really didn't want to play along. I thought of forcing him:

Zoe: William, you will marry that woman and break Isabel's heart so you can rush to find her later and have hot make up sex!

William: Fuck you.

Okay, he probably wouldn't have said that. More like: 

William: I beg your pardon, madam, but you are sorely mistaken. Get out of my way before I move you with force! *rushes to find Isabel*

So, my character's actions got in the way of the tension. This doesn't happen when the tension is internal (the character themselves if causing the tension by their own thoughts/actions), but external tension (tension coming from outside the character) has this problem. Another (almost book length!) male/male story I’m also working on has a whole lot of internal tension with some external tension thrown in too, but it seems to work out much better with the characters because the mix of tension is better.

I guess I've learned that having a strong internal conflict can only aid your story. Will and Isabel don't have one (and I apologize for that) but everything he does is what his character would do given the situation. Had he gone through with the marriage I felt I would have been betraying him- and I'm not a writer for Glee! (Musical TV show burn!)

What are your thoughts?