2.5 year child with behavor problems?

in the begining my husband and i were foster parents in 2012 then we we got call for a newborn born on nov 5 2012 she was a meth baby weighing at 4.8 born at 37 weeks we had till she was 8 months old then went back then she came back to us at 10 months because the biolocal parents relaps on drugs and domestic vilence in the house. so the socal worker said if you want the baby back her sister would have to go with her because her previouse foster mom did not want her and she needed to be with her baby sister. we did not know the older child all that well except thru visitation at child haven were the kids visit and see there parents once a week for an hour. so of course in our hearts we said yes because we did not want to loose the baby again even tho its only foster care but it will lead to adoption pretty soon. so we got both girls in foster care born 13 months apart both born subsence the baby was born on meth and the older child was born on oxycotten and pot those two were luck to come normal from the outside of there features. so on sep 9 last year we had both girls in our house for foster care and then on april 10 2014 we adopted them both. it was a happy moment at that time but i dont think we knew what we were getting our selves into. we did not know the older child all that well and as we got to now her it was quit ovious she has behavor issiues and does not listen due to being now 5 different foster homes . now how do i deal with the older one who gives me stress!!!!