Quoting Amelia Margaret:" Did two of them split? Or were they poor quality and/or 3 day embryos? How old is she? There is not a single RE in the US who would transfer 4 decent quality 5 day embryos. No way."
And they would be cramming it down her throat to reduce. They encourage healthy moms who have support to reduce with quads. The risk for loosing them all is HIGH. High enough to say you'd have a much better outcome to reduce by 2. More likely they transferred 2 - maybe 3 embryos if they had one or more of poor quality in order to end up with quads.
If it is true I wish her the best of luck. It is not a position I'd want to find myself in ever.