Are you sure she wasn't trying to peck you instead of the chicks? Some hens go into defense mode more than others. I have had issues slipping chicks under a broody hen in the daytime, but I removed them and put them back under in the dark and all went well.
Your hen sure is a strange broody.
You can do the following:
Get an all wire crate and put her in it WITHOUT any bedding. Give her food/water and put it up on cinder blocks to allow air flow underneath her. Several days to a week should do it.
OR..............................
get a couple day old chicks for her and slip...