Sister Marriage

Dear Sir, i got my sister married last year. we had adopted her and she was my aunt's daughter (Same Family). we had never thought that she is adopted and she grew up with us. we got her married and we did not tell the groom about the adoption. we agreed to whatever they asked as dowry grand marriage ceremony, bike, gold....everything they wanted. on day 1 of marriage some how they came to know that she is adopted and they started issues. we had a discussion with them and asked them if that is the problem then tell now only so that we can arrange some alternative things. but they said they wanted my sister and accepted everything. later they started telling that we (mom, dad all brothers and family members) should not talk to her and they broke all the contacts with her even they broke her cell phone. even if my parents go to see her they did not allow them inside and they would not talk nor call us. we kept quite as it was my sister's life. in the mean time she got pregnant and she was not sent to our home nor allowed us to see her...and all the 8 months she made her to work, cook, clean, wash all the we had bought her to our house since its near to her delivery. Now her inlaws have called and told us that they will not accept her and started abusing my sister in front of us. my sister is scared to go to her house as she has been abused by her inlaws all the time. my sister is emotionally scared of her... Now they have called and are saying that they will go legally. Its totally 9months of marraiage. Please suggest me what to do in this scenario. i want my sister to be reunited with her husband... they feel that we have cheated them by not disclosing them. but on day 1 only they came to know abt this and they accepted her. after that we had given them bike money what ever they have asked. Please suggest.