Intermediate Board Size

I'm sure this question has been asked a thousand times!!
I have settled on being a longboarder, I love the glide rather than the ride.
But my better half gets frustrated at the slow turning speeds of the bigger minimals so wants to go shorter.
From what I have read I think that she would be best off with a 6'6" or 6'8" Fish as it has the width and the bouancy to catch waves but has more manoeuvrability than a minimal.
We aren't rolling in dough, so our budget is £150 which puts us firmly in the second hand market.
However I have noticed that shortboards are ten-a-penny on auction sites and regularly go for £100 or less. But would a narrower (18" or 19") board be too flighty for her? Although I am sure we could sell on if she doesn't get on with one, but would rather not waste the cash in the first place.
Her dad has a Nigel Semmons Ocean Magic from the 1980's and she has tried that in the past but tells me that she didn't catch much, however that was a long time ago and she has improved a lot since then.
Any advice is gratefully received, (Jaffa?)
I have settled on being a longboarder, I love the glide rather than the ride.
But my better half gets frustrated at the slow turning speeds of the bigger minimals so wants to go shorter.
From what I have read I think that she would be best off with a 6'6" or 6'8" Fish as it has the width and the bouancy to catch waves but has more manoeuvrability than a minimal.
We aren't rolling in dough, so our budget is £150 which puts us firmly in the second hand market.
However I have noticed that shortboards are ten-a-penny on auction sites and regularly go for £100 or less. But would a narrower (18" or 19") board be too flighty for her? Although I am sure we could sell on if she doesn't get on with one, but would rather not waste the cash in the first place.
Her dad has a Nigel Semmons Ocean Magic from the 1980's and she has tried that in the past but tells me that she didn't catch much, however that was a long time ago and she has improved a lot since then.
Any advice is gratefully received, (Jaffa?)