No suggestions, but the "stomach virus" is usually Norovirus (that's what's going around right now), which is NOT treatable with "flu" (as in *influenza* yes, which is also going around right now) medications like Tamiflu.
If it IS Noro, the best (really the only) thing you can do is CLEAN, CLEAN, CLEAN! Noro is very stable in the environment and very easily passed around a household (fecal-oral route = poop, to hands, to surfaces/food, to next person)!!!
Right now she needs Lots of fluids (especially things like gatorade, powerade, things that replenish what's lost with the runs)! Usually Noro runs its course in 2-4 days, so she's probably just about over it! It's awful, so just be super careful to keep things clean (and kids away from mama's bathroom)!
Good luck!