I really like it. It's an old person sounding name though but only because it's not one you hear very often. 5 yrs ago, if someone said they were going to call their child Martha, you'd have thought Anne of Green Gables or similar wouldn't you?.
Gussie I don't like, August is more likely which is quite nice but who knows with kids, it probably won't be down to you. Would you hate it if she were just called "G" or "Gusty" ?
I love Elizabeth but don't like any of the derivatives much so I didn't use it.
This isn't v pleasant, though I can't think of any female saints that didn't meet a nasty death, usually at the hands of their fathers. Nice.
en.wikipedia.org/wiki/Augusta_of_Treviso
I'd go for it !