Listening to this clip on YouTube, right at the beginning she said aftermath with a BATH vowel in the final syllable.
Huh! I had always used TRAP there, as in maths. (But then, I’m not sure whether I’ve ever heard the word spoken before.)
Looked it up on dictionary.com; its house dictionary only has TRAP for the final vowel, but further down, the World English Dictionary has BATH (i.e. it lists both the TRAP and the PALM vowel, and in fact the PALM one first).
Since for me, BATH goes with PALM, perhaps I should use BATH in aftermath as well.