So wait you're trying to "program" her into being lady like? I don't have kids so if you feel my opinion is worthless I understand, but, just let her be herself and if that means being tomboyish so be it.
Why not let her join in? She could easily be better at this sort of thing than her brothers are. Give her a go at it for a day and she may not like it at all.
You could also throw in a curveball and maybe send her and her mother off some where to do lady things, just the two of them. I hope like hell when I have kids that they are interested in this type of stuff, regardless of their sex.
edit-just seen your reply above mine. I vote give her a day to see if she actually likes it or not. she may just want to be part of the group more than anything. If she don't like it I'm sure her and her step mother could find plenty of things to do together so she doesn't feel left out.