is she "really" pulling her hair out or is she just playing w it so much that it's starting to fall out?
is her hair long enough to pull back? If so maybe you can just pull her hair up in a pony tail or pig tails. If you decide to try this, I have found that when I'm fixing my daughter's (20 months) hair that I have to do it while she's sitting in her highchair and busy eating or make it part of her bath/bed time rutine.
If she's just playing w it to the point that it's falling out maybe she'll take to a "blankie" or something instead. My lil girl has her "Ellie" it's one of thos blankie type toys and it has a "silky" type edge that she loves to rub on her cheek. Or you could try a baby doll w "hair", maybe she'd take to playing w the doll's hair.
If she's "pulling" pulling it out then I don't know.
(my bath/bed time goes like this; first I get every thing that I'll need on the couch or floor [where ever it is that I'm going to sit down w her] and I have to kinda "hide" her Ellie [her favorite-go-every-where-with-her toy] Then we "go to the bubbles". When I pull her out and wrap her up I'll go sit down. Turn on Noggin or Sprout on the tv. Then I spray the detangler(sp?) in her hair, then I lotoin her, clean ears, clip nails, comb hair and if she doesn't have her Ellie by this point I'll give it to her while I fix her hair. Between Ellie and cartoons she almost always sits really still for me. I have found that if I put some moose in her hair then her pig tails will stay up for 2 or 3 days.)