FTP 13.5k guarantee late ATo on button

[fingersmith]

21 left, blinds 800/1600 ante 200. Just got moved to this table so no reads. 8 people at my table.

CO: 31k in chips
Me (button): 48k chips
Blinds: each like 20kish

Folds to CO, who opens to 4800. I'm on the button with ATo. My stack is 48k; I 3bet to 15 with the intent to call a push obv. I'm pretty sure this is an awful resteal with the stack sizes, but my hand plays like ass postflop and I didn't want to fold. What do you guys think.