I commend you for your love for your mother and your desire to honor her after her death. I pray to Allah to forgive her and admit her into His mercy and paradise. I also pray to Allah to forgive your shortcomings and failures, if any, you may have been guilty of while she was alive.
Now coming to your question, you can certainly do a number of things for her: The Prophet was asked by someone, what do i owe my parents, now that they are gone? He said: "You owe them to pray to Allah for their forgiveness, and offer supplications, fulfil their vows and pledges, strengthen their ties of kinship and honor their friends".
You may also offer charities as well as other righteous deeds while asking Allah to send them the rewards.
For further details, please consult the following answer.