So You're Flying Solo
Not only is she all you have, you're all that she has had; up 'til now, anyway. As a single dad you're playing the role of dad and mom to your daughter due to divorce or death. Whatever the case, if you long ago assumed complete responsibility for this child, you've taken the role very seriously. The discussion about other Fathers of the Bride doesn't really relate to your situation, because, quite frankly, you have more to think about than the dads who are simply going to walk their daughters down the aisle.
Realize that your daughter probably feels as protective of you as you do of her. She's not going to sprint down the aisle and out of your life; she's simply maturing and stepping into a fuller life, one that she's going to include you in. The alternative to this is her staying single forever — a viable choice for a woman who wants to be single, but a lonely choice for someone who dreams of having her own family.
Try not to think of her wedding in terms of her leaving you. You'll find (after the wedding) that your fears are unfounded, that you haven't lost a daughter — and that you really have gained a son-in-law.
Taking care of a child on your own is no small task. Of course, the benefit is that you may have developed a much closer relationship with your daughter than you might have otherwise had…which makes handing her off to a groom