Since you have an attorney and he/she has given you an opinion as to the anticipated outcome of this matter, I cannot and will not second guess his/her advice. If you do not trust your attorney's opinion, they is a different problem altogether, but if she believes that the father will be successful, that's the advice you should rely on.
My response is based solely on the limited information contained in the question. It is not meant to substitute your attorney's advice.
More facts are needed to answer this question. How long has father not seen the child. What is the general consensus of the judges in your court system. One of the factors that the court should be looking at to award joint custody and whether the two of you can communicate. However the court is used to dealing with no-communicative couples which doesn't necessarily prohibit joint custody. You might consider meeting with a Parent Counselor together to work on your issues.
Rely on the advice of your attorney, that's what they are there for.
Keep in mind, with almost all custody situations, the standard is the Best Interest of the Child. As I'm sure you are aware, legal custody encompasses those decisions you make for your child, such as medical decisions, schools decisions ect. The court typically will find it to be in the best interest of the child when both parents have a say in such important life decisions.