I am very sorry to hear the doubly sad news - of your mother's passing from this world and the cremation that your mother did not want. May God comfort you among the other mourners and may you know no more sorrow.
What can you do to honor her memory? I assume you have some good ideas of your own, but I would suggest giving some charity in her memory to needy families according to your ability in her memory and merit. Another idea would be to set aside a few minutes in your day to say a chapter or two of Psalms (Tehillim) in her memory and honor. Her soul lives forever and whatever mitzvah you can do to increase her merits will elevate her eternal existence in the Afterlife.