It may get old to have her little hands in your hair right now, but she won't do this forever.
She won't be 17 years old and refuse to sleep without her mom's hair... most likely anyway :).
Our son does the same thing with my hair.
It seems to be comforting - something that immediately soothes him and is a cue for him to calm himself.
Anytime he's upset and i'm around, the hands go straight for the hair - even if we're dressed up or at church or whatever -wet hair, dry hair, fixed up or messy - he's an equal opportunity hair messer upper.
I have short hair that's easy to deal with... that helps.
The way I see it is this -
I should treasure every time those little hands reach for me.
It really won't be long and they'll not be there reaching anymore and I know I'll really miss them.
As long as she's not pulling or grabbing, it seems like a good way for her to use her sense of touch to soothe herself.
It sure beats a million other things kids have to have to go to sleep.
She'll grow out of it eventually.
Just before she falls asleep, you could try holding her hand in yours... still in your hair at first and then moving it- replacing the behavior with one more convenient for you, but still meets her need for tactile soothing. You could also get her a toy with hair she can touch - the goal being providing a replacement for the behavior that still provides the same soothing touch.
Whatever happens, remember that she'll only be little for a brief time - then she'll be all grown up and you'll miss her needing you quite so much.