If I were Shadow's mom lol, I would encourage him to vent his thoughts and recollections about Maria in a good way, so as to avoid him अभिनय out any frustrations he may have and to ease his depression (if he still had it). For example, he could write down whatever flashbacks that came to him in a notebook - that way he could come back to those entries and could put the pieces of his memory and history back, bit द्वारा bit.
Also, I would encourage him to value the time he spends with the other Sonic characters as his friends, not to replace Maria but to help make new positive memories that he can cherish.
Can't think of anything else at the moment, except teach him to vent out anger in non-destructive ways maybe (without turning him into a sissy of course lol). Overall, I would want my son to heal any anger, hurt, etc that he has inside of him. (Image not mine).