Hi,
First of all I would suggest being less critical. IT very well may be that you're right about your step daughter's behavior but I think you should start from a different point. Try and spend time with her and get to know her a little bit better. I know this sounds hard but think of something you both have in common and work from there. Eventually you'll be able to influence her by just being close to her.
You should also talk to your husband and tell him about your fears. They are legitimate and these are difficulties very normal for such a situation. He should also try and help you get closer to your step daughters and should support you throughout the process since it's in his best interest.
I wish you the best of luck.