Why the 'reveal' at the end doesn't work (SPOILER)

The end reveals that the axe murderer is Lillian Nebbs, which deviates from the several possibilities up to that point. The killer being a female was done in the original "Friday the 13th" and "Happy Birthday to Me," 7-8 years prior, as well in future slashers, like "Urban Legend" ten years later. So the idea of a female slayer was nothing new.

While the killer being Jason's mom in the original "Friday" is believable for reasons I won't go into, I never bought it in "Urban Legend" for the same reason it's a weak reveal in this movie, only more so: Lillian is too petite, dainty and winsome to pass as a psycho axe killer who can axe down whole doors to get her prey.

There's a second reason it's weak: Earlier in the film we see a flash of the killer before putting on the mask & axing someone to death and it clearly looks like a male akin to Richard or Gerald. Sure, it was a quick, ambiguous flash so it was impossible to discern who it was, but it certainly didn't look like a petite female.

I still think this is a worthwhile 80's slasher up to that point. I liked the Big Bear Lake milieu and how several of the characters were fleshed out with some interesting bits, like Richard's cougar wife, as well as the emphasis on mid-80's computers.