STYLETHREAD -- LET'S TALK SHOP!

She has to be bold and tell him she is not interested in any romantic relationship.  It helps if she can act like she is interested in someone else, or even an idea of someone else.  She can always say it plainly, without spelling out what she doesn't like about him, "you are just not my type" or "I don't feel that way about you."  Or she could just tell him he is too intense, that used to be a major problem for me, I don't know why, but I attracted a few would-be stalkers because I was somehow too nice and they got the wrong message.  It is really impossible to be/stay FRIENDS with these kinds of guys.  It doesn't work, and you will find that those kind of guys rarely have many female friends who are single.

As for getting this friend out of life completely, avoidance works.  He probably just seriously gives her the ick and makes her really uncomfortable confronting him.  Some guys are just persistent like that and when they are, you dread even running into them, so maybe that's why she is seemingly afraid or desperate to shake him.