Sounds 'normal' given the circumstances. Hope mom will also be getting help for the child with someone skilled in dealing with early sexual abuse.
I would be more concerned (if one could be more concerned) if she were too affectionate, clinging to others, and acting towards males in a manner inappropriate to her age---as this might reflect an "acceptance" of the abuse as "normal", or "in her control".
Also hope mom can be there for her during this time with the help of a therapist; it is so important she does not feel that she has lost both parents...(but understand mom needs to do what is best for her in order to do what is best for her daughter) Glad she has a friend like you to provide support, and a home during this difficult time...and it is the beginning in many ways...