Other Middle East and Africa Frequent Flyer Programs - flying LY, choosing seats w/Matmid + crediting miles to AA: possible?

My fiance has an upcoming LY trip TLV-LHR-TLV. As apirchik pointed out in a previous thread, signing up for El Al Matmid ($20 a year) will enable her to choose her seat ahead of time, hopefully scoring her windows (or at least not middles).

But she probably won't take enough LY flights in the near future to make the actual Matmid points useful, so she'd prefer to credit the miles to AAdvantage, where she has an active account.

Is there a way to choose seats using a Matmid number, then swap out the Matmid number for the AA number so the miles get credited elsewhere? Or is that asking too much?

Ive known people who put the credit onto AA, its not mile for mile. I forget the % but not much ( heard 50 or 25 % of actual milesand No status miles). That was for flights from the States to TLV.
I would imagine as with US carriers in order to select a seat, do online check-in your FFB # from that carrier has to be on the record. I guess one can do that and then try to switch it at the gate, then call up and switch it back for the return Only to reswitch it at the gate again. Ihad this DL,CO,NW flights