Welcome Intrepid Wheelwoman, i am currently building a bike for my girlfriend and know how tricky it can be to do a ladies frame build while still being friendly to ride.
I also have a "mixtie" bike and considered using it but i didnt think a chinagirl engine would fit, nice work getting it to fit in there. I really really like it. I dont know how much work you are willing to do to it, but it would look absolutely awesome if you could make (or get one made for you) an inframe tank to sit above the engine.
I look forward to seeing what you come up with....
For my girlfriends bike i ended up using a Briggs and ladies mountainbike frame and modified it a bit..... heres where im at
Where im up to: