Lavinia Woodward, 24, attacked the man at Christ Church college, while she was under the influence of drink and drugs.
At Oxford Crown Court, Judge Ian Pringle QC said the "extraordinary" student might avoid a jail sentence as it would affect her career prospects.
But the university said the suggestion Woodward would return to her studies was "the judge's not the college's".
A spokesperson said there was "no guarantee" Woodward would be allowed back.
The BBC understands the medical student had previously been warned about her drug use and told she could be expelled if it continued.
Judge Pringle said he believed the attack was "a complete one-off".
"To prevent this extraordinary, able young lady from following her long-held desire to enter the profession she wishes to, would be a sentence which would be too severe," he said at a hearing on 12 May.
"What you did will never, I know, leave you, but it was pretty awful, and normally it would attract a custodial sentence."
The university spokesperson said: "A decision on continuing study will always take full account of the health, wellbeing and best interests of both the student and the wider student community.
"No-one outside of the college and university can guarantee the right of a return to study. No final decision has been reached or guarantee made."
During the attack on her ex-boyfriend, a Cambridge University student, Woodward thumped him, lunged at him with a bread knife and stabbed him in the leg.
She admitted inflicting grievous body harm and will be sentenced on 25 September.
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An Oxford University medic who stabbed her ex-boyfriend might not be allowed to return to her studies.