I like your gardening idea, k.
The only thing that worries me about it is when you get your first big job, you might find yourself a bit pushed for time to honour it! (I'm being realistic here!)
So my suggestion is a one-off gift. Perhaps of the plant/gardening variety ... like a beautiful pot plant (of the
not temperamental variety! :wink: )
Or perhaps something you've cooked or baked yourself (I know you're a
ripper cook!

) that she could take home & enjoy! Like home-made short bread, a jar of pesto (if this is to her taste), olives, or .... ?
If you have a good idea of her tastes in food.
Nothing at all wrong with a gift that's a wee bit "personal".