While the two passengers may be on the same PNR, each has his own ticket. If one passenger is a no show, it will not affect the other passenger (in this circumstance).
The friend should read the fare rules for his ticket carefully and not trust what Expedia tells him over the phone. It is entirely possible that the ticket can be cancelled and have some residual value and taxes may also be refundable as well.
That said, I would do nothing in advance. If the flight is substantially delayed or cancelled, the friend will be entitled to a full refund and may also be due compensation under Israeli or EU rules.