The idea behind this is that in special relativity, a moving body is heavier than a stationary one. So, if you had a star at rest relative to you and which was slightly larger than its event horizon, if you moved relative to the star, its mass would be larger and its event horizon would now increase to engulf the star just because you happened to be moving relative to the star.
Nice try!
But mathematically, the event horizon is defined by the rest mass of the star which does not change because of your motion relative to the star. The event horizon is a feature of the local space-time near a star, not a feature of some distant coordinate system.