People consider themselves normal so anyone not as “frum” as them is modern and anyone more “frum” than them is too yeshivish. Like everything else everyone uses it from their perspective.
There is a difference though between Modern ORTHODOX where they’ll wear jeans, watch TV etc. and still keep halacha. As supposed to MODERN Orthodox where they keep certain mitzvos or aspects (like they won’t drive on Shabbos but they’ll watch TV).
And back to the OP why should their be a problem if the girls behave and act with tznius? Why can’t they enjoy the fresh air too?