What is Blue Moon's stalker's backstory? (Every Breath You Take spoilers)

I just finished Every Breath You Take (walkthrough video).

To recap the mission: Blue Moon from Us Cracks needs your help dealing with a stalker that has been following her, sending her death threats, and even mailed her a bomb.

During the mission you'll find out that the stalker is a latina, Griselda Martinez. She approaches Blue Moon, identifies herself as Green Cloud, and asks to take a picture with her. Blue Moon allows this, and afterwards she remarks "Nice kid" as she walks away.

If you don't intervene, eventually there is a confrontation between the two, and there is some dialogue before Green Cloud shoots Blue Moon:

GC: “So you think I'm a kid, huh? I gave you everything! Everything!”

BM: “I don't even know who you are!”

GC: “United in life. United in death.”

If you take out GC, you find a journal of BM's daily activities and a picture of BM with the eyes crossed out on her body, confirming that she was the stalker.

So the question is: what is GC's motivation? Why is GC obsessed with BM? Why does she want to kill her? And what does she mean when she says “I gave you everything?” Did the two have a previous relationship, or is GC just crazy? What do you think?