Rubin's one of those weird ones. On one hand, she became the second woman ever to win the Royal Astronomical Society's Gold Medal.

On the other hand, she's famous because of something she popularised, not discovered, and anyone saying she "discovered dark matter" is misleading you, or has been misled themselves. It's a weird thing in science where the original discoverer of something is rarely credited with it until much later, and sometimes not at all.

Rubin's paper on galactic rotation curves with Kent Ford in 1980 was re-stating a discovery Horace Babcock had made in 1939, when he published the flat rotation curve of M31. Babcock still wasn't the first astronomer to come across the "visible mass deficit" as it became known, but did probably cause that name to be coined.

Fritz Zwicky, working at Caltech, used virial theorem to estimate the mass of the Coma cluster, and discovered a mass enormously "too high". The idea there is that you can use the velocities of the galaxies on the edge of the cluster to derive a total mass for the entire cluster, and Zwicky got results around five times too high. Zwicky's results are now considered to be accurate for the method he was using.

That the mass to light ratio was not unity was widely understood in the 1960s and onward, and Rubin's work was trying to find out why. She never did find out why, but that's fine, nobody else has yet either!