It's kind of romantic for her to still be loyal to him. I think that her ending up single for the rest of her life, while the others find love would be a good ending.
This has anime? I'll be sure to check that out after I'm done with the manga :D
On another note, Rikuo's going to end up with a cold, and both Shinako Nonaka will be looking after him, right?
I'm guessing the boyfriend was leeching off of her. We can see this when he gives her chips, a pachinko prize, and asks her when her next payday will be. When she gets pregnant, he disappears, because money will be even tighter to support the child.