Guru,you using AAPL as an example for the specified diagnol,but you are not using 100 as the spot price. You are using 126,of course the Vega changed and went negative... which is I specifically said foward ATM...Think bro..
You need to simulate the spread at different dates keeping spot at 100 and assume the Dec exp is shorter dated...
That's the only hiccup,and why I brought up large discrepancies for DTE and ATM foward..Not sure you are getting it
Read the question..Spot is at 100,long put is ATM (100 strike),short put is 110 strike,assume expiring 1 month earlier..
Thanks, finally you've decided to look at the question!

And you're right, I didn't use the 100 spot, so I'm the one who wouldn't pass such interview question. I could still argue about the dates, but at this point I'd have to agree the answer is long delta and long vega.
At least the OP may now get the right answer. Wouldn't happen without people actually looking at or discussing the question.
(CZR would be a good stock to test this with)