Is it permissable to perform Haj for some one else. has asked me if I would pray Haj on behalf of his mother's foi who died

Alhamdulillah I have prayed Haj at age 12. I was Baligh but I did not understand things well I also did not have a lot of insight. I am really grateful for the opportunity, however I feel that if I go now I will do much better. I have the means, I wish I could have another chance to do it better with greater understanding. My husband is thinking about going but he has asked me if I would pray Haj on behalf of his mother's foi who died. I do not know if she expressed any intention to pray Haj before she passed away. I don't know what to do. Please advise me. Jazakallah