That's an amazing deal for a cage that size!Even if she does outgrow it as a permanent cage it isn't like you couldn't reuse it for other things anyways
As for extra enrichment,try things like foraging toys which you can easily make yourself.You could also add different pieces of wood,extra hiding spots,or for an easy DIY you can make a small platform using a piece of safe wood and wooden dowels and just glue that together.
Just be creative and think in terms of natural behaviors that can be expressed through different things like burrowing,digging,chewing,foraging,etc!