Ok - here's what I think.... actually, I'll tell you what the voices say, they're better at poker than me....
When you're holding a small set pre (<999) the most likely holdings of your attacking opponent are:
As 2s x x (or equivalent - it only matters that she has the As + a deuce + one other spade)
or as I prefer to write it with her hand and the board:
(A2)xx
(5)
This gives you approximately 55% equity (see here), so your decision is an ICM type of one.
I've seen you play and I think you're good enough to fold - you have too much tournament equity to be flippin