Given both your weights and height, I would say the wide point are actually too wide an awkward for you. Regardless, Starboards are one of the better boards. In the longer boards I would be looking at the 10'5" Tiki and/or Drive, both at 30' wide. I have only tried the Drive, and it is a really nice board.
A good idea would be to get two slightly different boards. You could easily throw a Starboard 10' Noserider or 9'8 Element into the mix, both again 30' wide. For a good paddler on the flatwater and stability wise I would not go shorter than the 9'8". The advantage would be that it would be easy for your partner to handle, both in and out of the water, though obviously a little slower to paddle. If she is not particularly confident with watersports, go longer than the Element.
On the two different board option, I would.also have a look at the new Laird.10' Surfer and Hybrid in the bamboo composite construction. The Hybrid paddles especially well on the flatwater, and is a great option for your partner. Both are very stable for the given widths. Again, especially in the surf, this gives you the.option of playing around with different boards.
In any case, hit the flatwater till you feel confident and make sure you have fun!