Even if your friend has filed an FIR against her husband then also she can definitely ask for maintenance.
However, for maintenance of her and her child she have to file another case in the Court which have jurisdiction over the matter, under Section 125 of Code of Criminal Procedure.
Under this Section, the Court can order the husband to give maintenance to your friend and their child.
However, one thing that your friend needs to keep in mind is that the Court will not entitle her for maintenance if she is having adultery or if she refuses to live with her husband without any sufficient reason or if the husband and wife are living separately by mutual consent.
I hope I was able to help.