Wow how many did she kill? Jokes aside,
Technically, its an entire squad going at once, so I believe that your opponent is supposed to wait until you finish all your attacks
Battle Primer, Pg 8, Section 5.3:
"In either case, declare how you will split the unit’s close combat
attacks before any dice are rolled, and resolve all attacks
against one target before moving on to the next."
Your Hekatrix is part of your wych squad, all the wych squad attacks occur at the same time. You should've determined, after your pile-in, how many wyches would be attacking and how many attacks that equates out to. The only way that it would've happen how you described it, is if your Hekatrix was actually your Succubus, thus being a different squad than your Wyches.
Sorry mate, seems like you've been Bamboozled.
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