Ekaterina Karaglanova, who had recently graduated as a doctor, was found dead by her parents in her rented apartment in Moscow last week.
They had become concerned after the 24-year-old who had more than 85,000 followers on Instagram, had not contacted them for several days.
Prosecutors have now released a video in which Maxim Gareyev confesses to stabbing her "at least five times in the neck and chest".
It is not clear whether the 33-year-old had a lawyer present when the video was recorded or under what circumstances the confession was obtained.
He can be seen claiming that Ms Karaglanova had insulted his “sexual dignity” and “financial capabilities”, before later saying that he regretted the murder and would co-operate with the investigation.
Mr Gareyev admitted in court to having debts of 8 million rubles (£103,500) but denied that the murder had been because of money, newspaper Komsomolskaya Pravda reported. He claimed he had only seen Ms Karglanova once before the murder, which he said was "spontaneous".
Investigators previously said CCTV footage had captured a man entering the block of flats where she lived. They said his face was hidden by a cap.
Police said there was no evidence of a struggle at the apartment and no murder weapon was found at the scene.
She also ran a popular travel blog which had thousands of subscribers.
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