What Windy ‘says’ is wind forecast, not observed wind.
Then you mention ‘other monitors’, what do you mean with it? Are they the anemometers fitting on wind turbines? Or other weather models prediction?
Which weather model do you select in Windy? I hope you look at ACCESS the Australian model ?
You don’t say where you are precisely located, so I made a comparison with ACCESS forecast and a local WMO weather station, the discrepancy is not so huge:

But if you look at the other weather station showing 15m/s, Mount Buller weather station also WMO’s, the difference is much bigger. This is not an issue from Windy but from ACCESS, the weather model of the Bureau of Meteorology.