This poem always makes me think that there are some pains I will never truly appreciate having been born to the house of man. I can't say I've ever been a fan of the mirror but Plath gives it an insidious sense of villiany, like the vile friend that we continue to trust no matter how much it hurts us.
I have to question though, who the true liar is? Yes we can gaze into the inverted pool of the mirror and see every spot, line and the barely visible scar but that is not how we see each other. We look at each other beneath the streaming sunlight, in the semi-darkness of pubs and venues and in drunken capers beneath the moonlight. At which point do we really see the 'truths' of the mirror? Psychology has certainly found no evidence of this in our memories.
It's why I hate photographs, they never look true.
The final line of the poem is incredibly vivd, like some hag rising from the dark depths where only the angler fish and other obscene lightless creature reside, opening its maw of scattered remaining teeth to swallow some poor beautiful woman whole.