Is it read as /mɪstrɪsɪs/?
Or /mɪstrɪs/?
/mɪstrɪsɪz/, /mɪstrɪsəz/, /mɪstrəsɪz/or /mɪstrəsəz/
But I think you can also pronounce it with two syllables, the genitive being assimilated into the final /s/. Shakespeare did so for instance.
Those are spellings. I am saying you can pronounce them alike.
My question was about pronunciation, not spelling.
Still, you answered it. It seems that your pronunciation of this word is different from mine. I would not claim that I would pronounce three clear syllables in mistress's, but my mistress's is very different from mistress
I agree that pronunciation is the most common; I am just saying the other is extant.