I'm not an expert...yet lol but ornamental citrus trees always seem to go down well. lemon are probably the easiest to grow, along with calamondin (little orange fruits). tahiti lime are a tiny bit more challenging. all of these are widely available at a garden centre. They produce beautiful clusters of lovely flowers, their fruit (hopefully) tastes great, and even the leaves are used for seasoning - crush one up and they smell strongly of the type of fruit they bear.

That just an idea though - it might be worth asking your partner what her mums passion is. if she loves orchids and lilies she might not want fruit!

good luck meeting her, i'm sure you'll get along great!

danny