Ludmilla Doronina said in the letter that so far she has had to learn of what happened to her son, Aleksandr Dolmatov, through the media.
"No one from the Dutch side has met me to answer my questions," she wrote.
Doronina does not believe Dolmatov's suicide was "voluntary," the Dutch newspaper NRC Handelsblad reported Sunday. She asked the Netherlands' Queen to help with "independent research" into her son's death.
Dolmatov was arrested in Russia in May during a protest against President Vladimir Putin, Dutchnews.nl reported. One month later, he fled Russia and sought political asylum in the Netherlands, saying he feared for his life.
Officials denied his application because they did not believe his life was in danger, and he was put in a Dutch deportation center at Rotterdam airport. Dolmatov killed himself Sunday at the center, leaving behind a six-page letter saying he was guilt-ridden about his actions.
"Say in Russia this was just an accident. What drove me to flee Russia is my laziness and slovenliness over which I failed to study the new laws," he wrote.
"I betrayed an honest man, and I betrayed my homeland's security. If it is possible, transfer my body to Russia. Russia is stronger than any other country, and it will only be stronger."