Ok,
so the revised plan is:
my girlfriend and I will fly to Vancouver first.
Me on a one way ticket, her on a return.
I'll activate my PR visa, and she'll hopefully get a 6 month visa, long enough to do her yoga course. We'll be totally honest about what were doing.
We'll get a return flight to LA from Vancouver a week later for my friends wedding. Spend two weeks in California, then come back to Vancouver.
Do you think it's better if we book the flights and visa to LA while in Canada? Or do it in the UK before we leave?
Any thoughts on the viability of all this gratefully received.

Bozo

Re: flights - maybe look at expedia to give you an idea of costs. Quick scan for a week in Sept for 2 people flying direct from YVR to LAX is £487 ( on UK site ) or $780 CAD ( on CAN site ).
You may want to look at flying out of SEA to LAX, catch the bus from Downtown Vancouver to SEA-Tac or drive - prices on UK site £378 or $575 CAD on CAD site.
I understand you don't have to worry about ESTA part of visa into US, turn up at the border and pay your $6 USD if driving or bus. Guess if flying filling in forms on the flight over.

Sure someone else will clarify.

Hi

Actually before using Expedia etc. Try http://www.itasoftware.com/ it list most of the flights available but DOESN'T sell anything, just give most of the prices available and routings.