The problem is that she's constructed a story in her head, and no matter what he does, she'll interpret his behaviour to match her story.
The story is that he loves her, and is so in love with her that the strength of his feelings scares him.
So he doesn't call for six weeks? He's scared of the depth of his love and needs space. He won't be seen in public with her? She's special, and he wants to keep her from the threat of alcohol. He's actively dating multiple women? She's special - none of those women mean anything, he's just trying to recapture experiences he missed in his youth. He owes her money? He's in a tough spot right now, and will pay her back as soon as he can.
He could send her to the hospital with multiple contusions, and she'd still find a way to justify it.
You, me and the rest of the board know very well that he's using her, and his main emotion is probably "Woo-hoo! I can sleep around on her, ignore her for weeks on end, borrow money from her and not pay it back, and refuse to bee seen with her in public, and she'll not only put up with it, she'll make the excuses up for me!"
Unfortunately, as the friend there's not much you can do about it. You can try leading questions and comments, but it sounds like she's ignoring those nicely. You could try being blunt about it *once* to see if it gets through to her. You can refuse to listen to her talk about her pseudo-boyfriend.
But nothing you can do will make her break up with the jerk until she wants to. When/if she reaches that point, you can be there to help her pick up the pieces.