Mathilda was daughter of the musician Ficker at the Kungliga Hovkapellet, grandchild of the famous Swedish actor Andreas Widerberg and niece of the primadonna Henriette Widerberg. She was enrolled as a student in Dramatens elevskola with her sister Charlotta in 1828. She debuted as a child on the stage of the Royal Swedish Opera in 1829 and was contracted in 1834. She was counted among the most notable talents in the Swedish Opera of her time, particularly since the departure of Jenny Lind. she was described as a skillful coloratura soprano. One of her most remembered performances was a duet with Jenny Lind. She was made royal court singer in 1837. She retired in 1858.
She married a musician at Kungliga Hovkapellet, Fredrik Gelhaar, in 1836. Her daughter Wilhelmina Gelhaar also became an opera singer. Her sister, known as Charlotta Almlöf after her marriage to Nils Almlöf, became a noted dramatic actress.