Honestly, as long as you are consistent with the parents (on future applications), it won't matter. I would go with the parents on her birth certificate (which may be her adoptive parents). Who does she call mom and dad (even though her father and biological father have passed away)?
You shouldn't need a lawyer unless you have a complicated immigration issue, like previous refusals, criminal history, etc...
We (on this forum) are happy to answer questions and check document lists for free! We've had a fair few members seek this forum after being lead down the garden path by unscrupulous or ignorant lawyers...