No, that isn't true. If a gay man or lesbian wants to marry another gay man or another lesbian in a state where it is not allowed they are not choosing to not marry. They could grab their partner's hand and march to the courthouse wearing wedding garb with a ring and everything to signify their choice to marry only to be told they may not. That isn't choosing not to marry, that is being precluded from it based on sexual preference.
States have all kinds of laws preventing people from marrying whomever they please.
If we hear back from her, we can determine the reason why. You have made an assumption that it is because of sexual orientation. Your sexual orientation does not prevent you from marriage, it simply may prevent you from marrying someone you choose.
Some states do not allow people with diminished mental capacity to marry, some do not allow people with certain diseases to marry. I guess we'll have to wait to find out why.