Those three spaced periods ( . . . ) can indicate a pause or a hesitation, so using them in dialogue will certainly make your intentions clear:
“She had to try . . . don’t you think?”
However, I find that ellipses don’t always create the sensation of a pause as effectively as other techniques can. Also, ellipses don’t give the reader any information about what’s happening within that pause. And that can be crucial information. Often adding action can simulate the brief passage of time and indicate the nature of the pause:
“She had to try.” He sat on the couch and put his hand to his head. “Don’t you think?”
The action gives the question—“Don’t you think?”—a sense of resignation. If I made his stance and actions more aggressive, he may seem like he’s trying to bully the listener, or perhaps convince himself.
So, before resorting to those ellipses, consider whether bringing action to the pause will enhance understanding, create emotion, or bolster tone. Even these minute moments have an impact on the way the reader understands the story.