I don't know your space constrictions but I do know a dedicated filter area will be much more efficient. The mixing of filter and tank is a bad idea only because ive been there. If you could swing it I'd do the overhead sump with your tank and her tank in the space below the window. Just like before but a little taller with the filter above them. You could do it very nicely, black acrylic as wide and as long as you want put some plants in there that people can see through the window. Im just saying you did a really nice drawing so you've got skill with that, try one with two tanks with filter up top. I can see how your idea can work but will it be the best filter for both tanks? And don't you think she'd be really happy with a dedicated tank of her own not just some space in the filter area. Trust me I don't always look at every detail and I've slowly learned a lot in the last 14 year's of marriage, you think it's super but it's not and she won't tell you her true feelings for 3-4 years then all of a sudden you are a jerk.....and you never even saw it coming.
Either way I think it'll be a nice set up good luck!