Can't mount Windows Boot Camp & USB on a MacBook OS X Yosemite 10.10.2
MacBook Pro (Late 2011) = MacBookPro8,1

According to MacBook Pro (13-inch, Late 2011) - Technical Specifications this has a 8x slot-loading SuperDrive. 

You should use your DVD drive to install Windows.

According to the Info.plist for the Boot Camp Assistant, your model is one of the "PreUSB Boot Supported Models". The usually means if you create a USB flash drive installer by any method, you will not be able to boot from it.

You also have a one of the "PreUEFI Models". This means you should install using using a BIOS/MBR boot method.

In the event, you can not install using a DVD, you can try using Virtual Box. The instructions are given here. This will install Windows to your internal disk without the use of a DVD.