I found evidence that Margaret had a sister Mary Ann Forshey b. Oct 31, 1812 and possibly died Oct 6, 1838, parents Solomon and Mary Ann Forshey. They were baptised the same day in 1831. She may have married David Noel April 30, 1833. Source was Catholic Vital Records by Rev. Ledoux. Perhaps they nicknamed her Matilda to differentiate her from her mother, but I didn't find any specific reference with this family using the name Matilda.