DS definitely says 'Da-dee'; I had heard that it was easier to say this than mummy or whatever. However, he did create his own word for me - 'Amby' which he has definitely used more and said before Daddy. He uses it to ask for milk/ cuddles or if I am out of the room/ flat, he will stand at the door and say it in my absence, then say it over and over with pleasure when I return.
His first word was 'oof' (woof) - I wonder if on the whole, it is more likely that your daughter's first word will be a reference to something (probably quite simple and specific) to which you both refer - so it is more likely that she will say your parents' names if you use them constantly within her hearing in relation to them, and she understands the reference? We have picture books with a dog, and he clearly joined the dots between that dog and the dogs we see out and about, and my pointing and speaking in a consistent and straightforward way (insofar as saying dog and woof is what I always do when I see a dog but I say and do a range of things in relation to daddy). He said woof before he said any of our names, probably because 'mummy' and 'daddy' are used in a range of quite complex contexts whereas when you say 'dog' it is simply at the appearance of a dog. When you say your own name, or someone else's, you are usually using it in the context of a range of other things (feeding/ dressing/ cuddling/ doing x action etc.) which are sometimes and sometimes not exclusively related to the person (so it's hard for DS to dissociate the concept of mummy from the person with milk - so he's not sure if it's me or the milk he's naming. On the other hand, people say similar things to one another in a range of situations involving different people - saying bye for example - so it's probably hard to work out whether you are naming action or the person doing it.) So naming others is probably tricky, and it might be that daddy is easier to say but more significantly when to say daddy is clearly and understandably modeled by a baby's primary care giver.
I have to say, though, that simply saying a word over and over again is a pretty stupid way of trying to teach it - you really have to understand the context of a word fully before you can use it. Having said that, if you are the primary care-giver, then it's unlikely that your name will come first, because it's more likely that your baby will model something that you do. Although it is common to speak about yourself in the 3rd person to a baby ('Mummy is doing x) the baby is probably not clear about whether any person describing themself as doing x in that situation would say 'Mummy' or not. So I would take it as a mark of your daughter's special relationship with you that she will find it easier to do something that you do and conceptualise a reference that you make rather than a reference to you.