The video shows the mould vanishing in minutes, and pictures showing how the area looked before and afterwards are incredible.
The mum used affordable Mould and Mildew Blaster by cleaning brand Astonish, which can be picked up in Poundland, Amazon and The Range.
Leah added: "I sprayed it on the area then left it for 3-4 minutes with the windows open then wiped away with warm water."
Unsurprisingly, members of the cleaning group were impressed with the results and wanted to know what product she had used.
One said: "My windows are horrible at the moment. What did you use?"
Another wrote: "I was shocked to find my windows like this today too! Will definitely be opening the windows on a daily basis from now on."
While it's clear that the budget spray has worked miracles at getting rid of the mildew, it's still important to ventilate rooms to avoid it happening again.
The Mirror has previously explained how ventilating the house properly and using dehumidifies can help avoid damp and keep your home mould-free in the winter months.
If you're looking for more incredible cleaning hacks, a mum recently shared a brilliant tip to get rid of stubborn stains on whites.