Yes, I did this with my partner. IIRC we had to call AA for the QF record locators, then you can go online and pick the seats on Qantas.com, or the AA agent may be able to do it for you, just give them both the AA locators. If you access your record on Qantas.com and you're logged into your QF account, it will replace your AA FF# with your QF#, which may be an issue if you have AA status but not QF status.