Ok, my description is going to be vague to say the least.
But theses are some scenes I recall.

Pretty sure it's an american film, b&w obviously.
It's from memory about a male teenager (16-18) who befriends an older female artist (painter) who lives in his apartment.
The artist takes him under her wing, educates him in art, life, love, etc.
Ultimately he becomes enamoured with her to the point of obsession.
Unknown to him she really only sees him as young friend/protege.
This becomes totally apparent to him when she introduces her fiancé.
The young guy is now in a world of hurt...

There is an elderly lady who also lives in the apartment(could be related) that officially introduces our young whipper snapper to a teen brunette that also lives in the apartment . She tells him that he should look for love in his age range and forget the artist (he had often spoken to her in the hallway and she undoubtedly had feelings for him, as she prepared him food or cookies to garner his interest on a few occasions ) but (jon doe) wasn't romantically interested @ that time

Something snaps in our young man. (the rejection, possibly) but he know has fallen for the teen brunette...
They start hanging out,
Spending time together.(his obsession with the older female artist is a distant memory) his new girlfriend is all he can think of.
Now... this is the vague part.. the young teen brunette has taken ill.
She subsequently dies, illness of some sort.
Our young man is beside himself with grief, it's torn him apart to the point
Where he's standing on the facade/rooftop of his apartment block.
As he's looking downward to street below, there are beckoning cries
For him to reconsider, he mentions something that borders on the prophetic, then jumps to his end.