Boy meets girl, boy likes girl, boy stalks girl??

It has been brought to my attention that instructions say to write 200-250 words per blog post. While I would really like to write more (and sometimes would unintentionally), I apologise to you who have had to trudge through too many words and would try to limit myself in the future. :>
Now for the real(ly) hypothetical situation

Resolving Interpersonal Conflict (Post #2)
To connect with you the audience, I have decided to use a romantic drama. That just means one in which there is a boy, and a girl, and one or more like each other, with a hodgepodge bag of spice thrown in in terms of a conflict. I am quite sure that university students would have encountered such a situation in one form or the other, whether personally or vicariously through peers. This plight is based on actual events, but the names of the lead characters have been changed to protect their identity.
Boy K and girl D have known each other for about a year now. Their acquaintance developed from attending the same co-curricular activity. They only recently got to know each other better and on a more personal level through a mutual friend (who is overseas). Both are foreigners, but D has been in Singapore for almost a decade now, while K has just arrived within the past year or so. D is pretty (much a friendly person), outgoing and sociable. She has more or less internalized the local culture, speaking singlish fluently and thoroughly enjoying the food here. She has been to the country where K and their mutual friend originated for a summer program. Therein lies the reason for their mutual friend’s asking her to bring K out in Singapore.
K has not been around Singapore much even though he’s been here for almost a year. He’s relatively quiet, preferring to concentrate on studies than social activities, and overall is a thoughtful person you would describe as a “nice guy”. He is overweight, but not overtly so. Financially speaking, he is well off but not rich (sort of middle income kind).
Now, after the outing, K keeps calling D, approximately twice a day. He also sends her gifts and frequently wishes to meet up with her to “spend time together”. He has followed her to her home and to her lessons as well. Efforts on the part of D to communicate displeasure have seemingly fallen on deaf ears. Obviously, D is feeling stressed by the hounding, and feels increasingly frustrated.
What might have gone wrong in this situation?
PS: Feelings of K have been intentionally left out until some comments have been made.
PPS: Perhaps focus on what has been given in the framework about the characters’ backgrounds.