If she really cares about this guy, she needs to make up her mind. Either leave the dubs and have an honest relationship with the boyfriend, or stay in bondage and release the guy. He doesn't deserve this.
Having been in his shoes, I know it's a really difficult situation. Even if they agree to respect each others' beliefs, there still will be conflict between the WT teachings and the relationship. In the organization's view, she must bring him into the congregation if they are to be married, and maintaining the relationship while not being married is out of the question. If the lady's mother does turn her in to the elders, the BOE will likely force her to choose between the Witnesses and the boyfriend as soon as they can round up a lynch mob judicial council.
Babygirl's friend really needs to talk this situation out with her boyfriend, if she hasn't done that already (I hope she has!). Unless he's had first-hand experience with the Witnesses, shunning, etc. he probably has no clue how intense this will be. They need to face it together, or it could split their relationship apart. Not being up front with the WT situation will undermine their trust and respect for each other, and loss of trust and respect sucks the life out of a relationship. Consider the usual cult tactics; they're all about killing trust and respect for outsiders and imperfect insiders: that's how they control you!
I suggest they should read the articles on Freeminds.org, together. Especially those on shunning, women's issues and marriage.
Babygirl, what you're feeling is the aftermath of the emotional bullying you knew in the WT organization, as many others have said. Don't feel guilty about talking to your friend and helping her out. That's what real friends do for each other!
Keep being good to each other. In the end, that's what matters the most.