If its a concern write her a 'social story' and read it with her several times. Social stories are the general way to assist Austistic children with learning whats appropriate. Its could be she's just playing, maybe she's seen a boy and is wondering we may never know but if you are concerned create a little booklet and read it with her, have pictures of socks on feet.

Hi
Before i give my thoughts think what you would do if your daughter did not have autism and developmental delay.  Would this behavior worry you?
Did you not put socks in a bra as a child and parade around
All she is possibly doing is being a child playing
Does she know why she does it....
I wouldn't panic
My daughter did it a few times and she has no known disorders...
But who knows try the stickers and it might make a difference
But most kids will do strange things now and then....
Luv Deb

I would try and work out why she puts them there b4 stopping her I am sure she has a good reason.  Good Luck.

Kastol

Could you possibly make sure all the socks are out of view etc? try keeping them in a mesh laundry bag out of her reach.What about exchanging socks for stickers/treats each time she gives u the socks give a reward.is there a way of making the socks less appealing?I hope I have helped a little.regards Merle