I agree with the others that it's personal preference. We went for a boy because we didn't want to have a girl spayed if we could help it (due to difference in coat, risk of aneasthetic and surgery, tendancy to gain weight etc, although we would have done so should it have become necessary for her own health). We also didn't know what to expect with an unneutered girl, like how much blood, and whether we'd have all the strays in the area hanging round. So for us it just made sense to get a boy.
I would have quite liked a girl so I could buy her pink bowls and blankets and collars
and I would have liked a sweet girly name like Tallulah, or Maisie, but we had to think practically.
I would see it as a good thing that she has questioned your motives as it is a sign that she cares about the puppies and their futures.
As for the anxiety of choosing and getting our dog - oh yes! Been there done that. I was posting on this site every minute asking for reassurance I'd done the right thing.
Thankfully everyone here was very patient and I learnt so much from them. I think having a bit of anxiety is a good thing because it motavates you to learn as much as you can and do the best for your pup.
Good luck with choosing
xxx