How big is her garden and does she have any particular intentions for it?
A trowel and spade seems like a good start. You could get her a handfork, a rake, some fertiliser for any vegetables she might want to grow (Tomorite is pretty good and not just for tomatoes!), some slug pellets and one of those nifty corkscrew-shaped weeders too. Packets of seeds are also pretty cheap!
(I'm trying to think about what I end up using when I'm gardening! I don't do enough of it...

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