Do you know what vaccine she got, Pfizer or AZ?
It's the way they're doing it in the UK.
AZ - the evidence, which is now getting built up and expanded on more and more, is all there that 12 weeks spacing makes the vaccine more efficient than it would if the doses were spaced out over 3 or 6 weeks.
Pfizer - the manufacturers have warned to stick to 3 weeks spacing inbetween the doses as that's all that was tested. The UK have gone with 12 weeks in the hope of getting more protection to more people sooner. France and Denmark have also used this method, but are going with 6 weeks instead of 12. There is no definitive evidence that either of these approaches are wrong, there just isn't evidence to say they are correct either. However, there are now studies which have been completed and will be under peer-review in the coming days/weeks, which the evidence so far seems to show the Pfizer one doesn't actually kick-start any protection until around 15/16 days after the jab. By 21 days, the protection is up at 90%. This would suggest that longer spacing between the Pfizer doses isn't an issue but, and this is where there is a lot of fair argument against doing it, we just don't know for sure. Once these studies are peer-reviewed in full, there'll be more information. As it stands, it's basically unexplored territory.