Problems on rigging a clothed shoulder

Hello everyone. Latelly,I´ve been rigging a human character - a female one - who wears only panties and a bra,and I´m having a serious problem now rigging the shoulder,which is covered by the bra´s strap,and there´s the problem: The damn strap! when I move the shoulder bone upwards(or in whatever direction I choose),it doesn´t follow the shoulder movement appropriatelly and/or pratically stay in place(right now,the bra is a separate object,but I´ve tried joining it to the rest of the body and skin them all together,but it didn´t really worked)
Here are some screenshots that illustrate what I´m saying,as so as,if it came in handy in order to know how to solve it, the blend file itself(it´s quite a mess,dont mention it). Thanks in advace!

screenshots:


.blend file:https://drive.google.com/open?id=0ByhNUKicqDu8RlFoMTJLWUlxbUk

I’m new to rigging so you’ve probably done this already, but are the vertexes on the strap assigned to the vertex group too?

Hey Lullip,thanks a lot for answering. Yes,they are

Just so you realize that you are using the meta rig for rigify instead of generating your rig. You may need to review a rigify tutorial. Here’s a good one for you. https://www.youtube.com/watch?v=2k9Hk8gpHKk (if you get stuck Dan is on the forum a lot or any one else can help.) But to get your separate clothes to work after you weight paint your main character, (assuming your vertices are matching fairly closely), just use weight transfer. Here is what I would do. First select your bra and separate it again into a piece all by itself. That way your auto weights will work on your main character. Next delete all the vertex groups on the bra. Re rig your main character correctly and weight paint it till you are happy with the movements. and your deformations. Then simply transfer the weights from your main body to your bra. To do that, select your main body, then your bra, then Switch to weight paint control tab. Hit transfer weights. In the transfer panel set source layer to by name. destination all layers, mix mode replace, mix factor 1.0. Hit the weight transfer button again. Back to object mode then try it out in pose mode.