Slominer – I don’t think I know of any Ashkenazi Bais Yaakov girls from this generation who are called by an english name. I do know Sefardi Bais Yaakov girls who go by an english name. I had just assumed that it was just as common amongst Sefardi boys, but maybe it’s not. Are you referring to Sephardim or Ashkenazim?
If in fact it is true that it is more common amongst girls, I would guess that a boy is more likely to feel uncomfortable in a Yeshiva going by an english name, simply because a boy’s school is a “Yeshiva”, and a girl’s school is generally viewed as a “school” as opposed to a “Yeshiva”.