Change iMessage font size on iPad

My iMessages works fine on my iPad and the text is normal. On my friend's iPad 2, iMessages is with realy big font size. That's weard and I can't find any option to change it.Unfortunately, iMessages app doesn't offer this option. But you can do that using the accessibility features. * On Home Screen, tap Settings > General > Accessibility.* Check "Large Text", and select your desired font size