80s Canadian? Thriller (Solved)

[Bargle5]

Saw this back in the 80s on HBO or Showtime. Main character is a teenage girl, though too young to drive. Supporting characters are her mother who is widowed or divorced, her best friend is slightly older and is sexually active. Male character is either courting the mother or has married her recently.
Male character is plotting to to kill the mother, though I don't remember why. Possibly for insurance money. Somehow teen girl and best friend find out what's going on and start trying to expose the man. He runs over the older friend, killing her. The main girl gets around mainly by bicycle because she's too young to drive. There's a scene with the older girl in bed with her boyfriend when the main girl walks in on them. We see the older friend topless briefly
I want to say it was set in the Pacific Northwest area, but I'n not certain.
I want to think the girl playing the older friend was well known at the time for playing nude scenes.

It's not "The Stepfather"

That's all I've got

[alyxstarr]

Maybe Scream for Help (1984)?

[Bargle5]

Right again, Alyxstarr! Thanks once more.