I have a Savage 1899 in .303 Savage.
Factory ammo is no longer generally available here in the US, but is a popular cartridge in Scandinavia and Europe, as well as Australia. Sometimes you can find brass for it on MidwayUSA or other such sites.
Reloading dies can sometimes be found from Redding or Lee.
Ammo can be reloaded, using data for a .30-30, best to start light, say 10% reduction, to see what your gun will take. They generally like heavier bullets, the original factory loads were 180 and 190 gr. Factory pressures were higher than for the .30-30 also. You will see some that say the bullets have to be .311, but that's not so. Some factory rounds were loaded with .311 bullets to increase chamber pressures and get more velocity. However the bore is .308 and modern .308 bullets work fine. With the rotary magazine you can even use pointed bullets, but they don't look right in those old guns.
There are several websites and forums devoted to the Savage 99 rifle, and the .303 cartridge, now more collector's items than shooters, but many still shoot them, as do I. A browser search will turn up some good places for info, and reading through posts there will provide others. Lots of fun shooting the old timers, and making ammo for them. Hope she enjoys the treasure she was given.