Q.) Is it permissible for a woman to perform Umrah with her friends who are travelling with their mehrams in a group?

A.) According to the Hanafi school of thought, a woman can only travel
on a journey of more than 78 kms (about 48 miles) be this for Umrah,
Hajj or otherwise, if she is accompanied by her husband or a Mahram
relative. Mahrams refer to those males that are perpetually haram for
her to marry, like her father, grandfather, brothers of her father and
mother, sons, grandsons, her brothers, and sons of her brothers and
sisters.
Hence if the woman concerned does not have a mahram then she cannot
travel in this way i.e. with her friends and their Mahrams.
And Allah Ta'ala Knows Best