Might try going to a nearby garden center or nursery and have them design a small area of perennials that attract hummers, maybe even add an angel garden statue to it.  Usually those places will come out and plant the area as well, for a small fee.  Perennials are low-maintenance and look really nice for a long time.  That way, if you have the basic design in hand, you can start small and then add to it each year easily.  Could take care of several future birthday gifts as the hummer garden enlarges. 

Good luck!  And happy birthday to her..........you're doing good to be thinking ahead on this.