Hmm...you know, I think to an extent it's possible to incorporate a naturally more shy and gentle person's nature into handling a stalker -- but when the only real solution is really either fight or flight -- Athenian's suggestion of quietly moving away is the easiest solution. Easy meaning totally conflict avoidant. It may also set up a bad habit in your friend's life and train to be so super avoidant as to be really debilitating.
She could also try pressing the police to act. Gathering more evidence, raising a fuss. If the police in your area/country are similar to police in the states, persistence and trying to talk to different officers can help. Eventually you may get lucky and reach someone who 1) actually cares and 2) is competent enough to help.
I do understand where Alcearos and Jennifer are coming from and I sympathize with the fact your friend's nature is very kind, gentle, etc. -- but I also know that in females this kind of character is TOTALLY a prime target for sexual harassment and in general being taken advantage of.
There's a reason why self-defense classes for women focus on screaming and yelling and basically feeling entitled to being "incredibly unpleasasnt", assertive, and in your face as the first line of defense against violators. That's pretty much the only tactic (I know of) to stopping potential attackers -- though you can also be humorous about it in some situations. If there were a way for her to draw public attention to the man's unwanted behavior and make light of it, that might work. However, this guys seems like he might really be crazy -- in which case it's a powder keg. True predators rely on shame, fear, and timidity to railroad victims.
The only practical thing I can think of for your friend is to get a dog and carry around a video camera with her at all times. In the states any physical contact that is unwanted is battery and touching with the intent or threat of physical violence is assault. Also in the states, even without 'evidence' -- like bruising or a witness, you can still file a complaint. The police may not be able to arrest anyone, but you can start a record of events. And technically the police are allowed to give stern talking to's and warnings to people. Do police in your area also do that?