Wouter, found your mast weight comparison interesting.

"If righting is a important point for you than your choice of boats narrows down very quickly. You should be able to right A-cats and M18's without much effort at your 70 kg.

I`m at 70kg myself, my mast is 9,5kg (bare section), probably close to 14kg fully fitted, similar to Shadow, BUT it is 700mm shorter at 7,3m. This makes the righting moment better for a 70kg crew. I can right my boat solo in all conditions, but I`ve had to stand right on the tips of my daggerboards on some occasions, so I seriously doubt Sarah will be able to right a boat with the same mast weight but 1,2m longer as the righting moment changes with longer mast.
Of course that`s my personal observation, and my technique may not be the best (though I`ve refined it from years of capsizing often - I think 4 in one race qualifies me as experienced )
Perhaps she should be looking at a smaller, lighter boat like the Shadow, has a very good rating for it`s size and she should be able to right it alone.

Sarah, not trying to put you off a 17fter, just need to know that when sailing it alone you might want to keep the rescue boat within reach - 2up you won`t have trouble righting, just when alone. A bit frustrating when racing to always need outside assistance from a capsize, as you`re then dsq`ed from that race. You will just have to refine your sailing technique so that you don`t capsize often, or sail with crew.
Good luck on your choice.

Steve