^The ACLU probably won't be able to help you. They're a pretty cool organization, but they take cases involving large groups or involving an individual whose case will impact a lot of people. You get my drift? They take on stuff that will have an impact on a wider scale. Your case involves only one one person and will impact only her and her shady inlaws.
However, it still might be good to give them a call since they have awesome contacts...they probably won't take the case, but they'll know of local attorneys, legal groups, or even big firms (with pro bono departments), that will be able to help you.
And - dunno if someone has mentioned this already - but DOCUMENT!!!!! Tell her to start recording every shady incident, every instance of abuse. Write down who, what, when, where, how, why. If Allah forbid, she's physically abused, find a way to take time stamped photos of cuts, bruises, etc. Retain copies of emails, letters, etc. If it's possible to tape (audio or video or both) an incident or phone call, do it. I don't know where you are and whether that jurisdiction allows tapes into evidence, but it can't hurt to try. Worse comes to worse, it will be thrown out as evidence. Be aware of anybody who is sympathetic to her and may have seen her being treated badly. They are your witnesses. Has anything ever been reported to the police or other authorities? If it has, call them up and get a report of the incident. Nothing impresses judges more than a good, clear explanation of the facts.