Doppelganger 1993 starring Drew Barrymore. Can horror fans explain the ending to me? WTF is Drew Barrymore supposed to be?

https://youtu.be/sDwtioa7NO8?si=YPKuRGmtTlZL_2Yw

She's some kind of giant worm?

I found this movie on Tubi. I've never seen it before. It's kind of stupid, and slow and boring...until the last 20 minutes when it turns into a David Cronenberg body horror. That scene alone makes me love this movie.

Drew Barrymore was only 17 when she filmed the sex scene and the shower scene. I don't know how to feel about that.