Angela Gilsenan was the foundress of Burnley, Lancashire. She joined and made her profession with the Sisters of Mercy in Tullamore. She gained an early experience of establishing foundations by going to Loughrea, and later she was part of a founding group at Commercial Road in East London. There, she was chosen to lead a group of three to make a foundation in Burnley, Lancashire. As a young sister, she had served as Teresa Purcell's assistant. This, along with her engagement with foundations, suggests that she was an extremely skilled administrator and organiser.

Brigid Gilsenan was born in Kilskyre, Meath, to Michael Gilsenan and Mary Connell. She joined the Sisters of Mercy in Tullamore in 1842, several months after Catherine McAuley’s death.

Angela joined the Sisters of Mercy at Tullamore, where Catherine McAuley's companion, Mary Ann Doyle, served as her first superior.

It is possible that Mother M. Angela learned a great deal about Catherine's motivations for founding the Sisters of Mercy from Mary Ann Doyle.

Mother M. Angela was very involved in the field of education. In addition, she established projects encompassing a wide range of works of Mercy.

In Burnley, Mother M. Angela faced a situation in which the government threatened to stop all grants to schools unless there was significant improvement in results before the next annual examination. Within a few months, she achieved the required improvement.

The Sisters who joined in Burney would eventually become part of the Institute of Our Lady of Mercy Great Britain.