Nice pouch. Wet-molded leather looks really good when done right, and it'll be sort of stiff, as you said, but it should work well for a sporran. Just make sure to explain to her what you want before she starts. Once you cut leather, there's no going back, and you could save her a lot of trouble by being clear up front. (voice of experience speaking).

Make sure she knows how deep you want it (front to back, top to bottom), and you should be fine.