Hmm . . . I've got a pretty little female. When it comes to prey, she prefers to "sting first and ask questions later," so I don't advise putting any fingers in range.
If you mist the side of the tank every few weeks, sometimes you may catch it drinking the droplets.
My female also seems to like exploring at night . . . make sure you have a good lid!
Fatness isn't always a sign of being gravid. The below picture was my girl back in early January. I think she was just well-fed.
Granted, she wasn't quite as "blimpy" as some gravid scorps get.
Also, are you sure yours is a female? With most Parabuthus spp. the best way to tell is by a little "nub" near the base of the pectines. I think there's a good photo somewhere on venomlist. The only pictures I have aren't very clear.
Good luck with it! These guys are really fun to watch when they're hungry.