Ohhh heck, if your friend doesnt like being the centre of attention, then a 'party' is off the radar, but you say she so deserves recognition, yes, then as others have suggested, a lovely afternoon tea, somehow get the name of 1 member of each group and ask them to spread the word to the others in their particular group. You can do this easily if your friend is on FB ( and ofcourse the others are too )
A lovely afternoon tea sounds ideal, everyone together for a special friend and yes as someone said, if your friend has AC, then it needs checking if they are planning anything.
Whatever you do, i hope your friend has a ☆☆☆FANTASTIC BIRTHDAY☆☆☆