I can't say I ever followed Marie Severin's career closely, but she was a talent I took notice of primarily because she was one of the only female comic book creators of the 50s/60s who people remembered, spoke of, and was still in the business. Much of her early career was spent as a colorist and she became not only one of the few lauded female comic book creators, but one of the few lauded colorists in the business. Her work coloring for EC Comics in particular has been lauded again and again. I certainly appreciated the effort she went to recently to recolor some of her early work for the Bernie Krigstein collection Messages in a Bottle (that's Reed Crandall art above, colored by Marie Severin).
Marie Severin put in a lot of time as an artist on Marvel's Sub-Mariner and Incredible Hulk, although she seemed most pleased to tackle humour. Above is a cover she drew for Marvel's Tower of Shadows, one of the earliest places I saw her artwork.
Her brother John Severin was one of the greatest inkers comic books have ever produced. There were a few times where the siblings were privileged to team up on projects, such as the Kull comic above, penciled by Marie & inked by John. In interviews, Marie would frequently call those Kull issues her favourite experience working at Marvel because was working with her brother. She was a talented woman and by every account an extremely likeable person. Rest in peace, Ms. Severin.