Sorry, that's bad use of pronouns on my part. What I was trying to get across is that the effects of gravity a star, or gas cloud, or whatever feels is mostly not due to the central black hole. The star feels forces of gravity from all the mass interior to its position in the galaxy. For example, our Sun is 8 kpc away from the central black hole, SagA*. Even though SagA* is massive, we're just so ridiculously far away that the force of gravity exerted by SagA* on the Sun is tiny. Instead, what keeps the Sun orbiting is the force of gravity applied from stars and gas closer to the Sun. So increasing the mass of the central black hole would have almost no effect on the Sun's orbit, and the same goes for most the stars in the galaxy.