She lives in Camden, north London, where property prices begin at pound;120,000 for a studio flat.
That is twice the amount she could expect to get on a mortgage based on her pound;21,000-a-year salary.
She currently pays rent of pound;715 a month on a flat within walking distance of the Maria Fidelis school where she works. That is more than half her take-home pay.
Ms Watson, 33, took a pay-cut from her career as a private-sector PA to become a teacher. She said she would sooner quit teaching than leave London if housing costs continue to rise faster than pay.
"I love my job, but at my age I should be earning a lot more. Maria Fidelis has lost 10 staff in the past year," she added.
She called on nurses to join with teachers in an action to demand pay-parity with police, who receive a pound;6,000 London allowance, twice as much as teachers.
"Really we need to be on salaries that match those in the private sector to give us a chance of competing in the housing market.
"I am struggling completely, which makes it a lot more stressful workwise. I qualified as a teacher two years ago so I missed out on the pound;4,000 'golden hello', which I'm a bit miffed about. I'm up to my eyeballs in debt. The only way I could save money is to move out to outer London, which would defeat the purpose."