Reward flight question

I've just tried to book a UC reward flight for myself and her indoors.
The good news is that they have still have reward seats to LAX and back from SFO in UC for our preferred dates[y].
I have enough miles for this flight , but her indoors only has enough miles for the outbound journey.
She was after a reward seat outbound and we were expecting to pay for a Z fare for the return leg.
The bad news is that VS quoted us £3000+ for the return leg. A 'Z' fare (return) is only £2500[:?].
I queried the £3000 and was told that I am not able to purchase a one way 'Z' fare in conjunction with a reward ticket and must buy a flexible ticket.
Is this correct?.
Do I have any other options? I have read that I could purchase a PE ticket and use 40000 miles to upgrade to UC.
Does anybody know roughly how much the PE fare would be to LAX returning from SFO. Dates, last week in June to 2nd week in July.
Your help is most appreciated.
Tim & Chris.
The good news is that they have still have reward seats to LAX and back from SFO in UC for our preferred dates[y].
I have enough miles for this flight , but her indoors only has enough miles for the outbound journey.
She was after a reward seat outbound and we were expecting to pay for a Z fare for the return leg.
The bad news is that VS quoted us £3000+ for the return leg. A 'Z' fare (return) is only £2500[:?].
I queried the £3000 and was told that I am not able to purchase a one way 'Z' fare in conjunction with a reward ticket and must buy a flexible ticket.
Is this correct?.
Do I have any other options? I have read that I could purchase a PE ticket and use 40000 miles to upgrade to UC.
Does anybody know roughly how much the PE fare would be to LAX returning from SFO. Dates, last week in June to 2nd week in July.
Your help is most appreciated.
Tim & Chris.