Hey Dominique,
1) The easiest would of course be to log out immediately when the user presses the reset button in the native app.
2) If you have control over the webpage where the user can reset their password, you could trigger a deeplink to the native app and handle it with the logic you need i.e. log out. This only works if the browser is opened on the same device.
3) Consider not using a webpage but a microflow call to handle the password reset from the native app.