Re: Now my wife wants a board
I agree with tony - you may as well buy one long board (8ft6+) and another board that is 8-12 inches shorter (so maybe 7ft10) and then you each surf the boards and pick the one you want. If you think the longboard is too long, you have a shorter board to switch to (or at least use now and then).
Or, of course, buy the longer board first and see what each of you think - about right, too long etc. Then pick a second board based your responses (same length, shorter a bit, much shorter etc). But don't fall into the trap of thinking that because you are struggling on the long board (eg perling) that a shorter board will cure the problem. In fact, in almost all cases the shorter board will make the problem worse no matter what your brain may think is logical (eg: perling, or nose diving, is not caused by having a board that is too long. Making the nose shorter would appear to logically reduce nose diving, but doesnt because the length of the nose is not causing the issue).
If you know what you are doing, 90% of the time you dont need that much strength to control a board in the surf; the other 10% of time is when you get hit by a big set or are in the wrong place or whatever. And there probably isnt a huge amount of difference between an 7ft6 board and an 8ft6 board if you are in that 10%. As long as your gf is able to turtle roll and get the nose under the water - which she should at 60kg+ even on a larger board - then its a non issue.
To be honest, I think you pick a board to learn on, then buy another board to advance on or learn different skills on. Its not really a sport where you buy one board for life. If you take this view, then the first board should be long and thick and wide; then you get another board. Better to start off too big than too small.