On The Flash, Dr. Wells and his daughter Jesse returned from Earth-2 to reveal that Jesse is a speedster just like Flash, Reverse Flash, Zoom, Kid Flash, and The Rival (just to name a few).
Apparently the dark matter that struck Jesse and Wally last season finally caused one of them to gain superpowers. Jesse came back to Earth-2 so she could run some speed tests while her dad said "Not" jokes, which were popular in the mid 1990's.
It's a good thing they came back because Quick Jesse, as her father call's her, was an integral part of fighting off the new villain, Magenta. Magenta was an abused foster child who Alchemy transformed into a metahuman with the ability to control metals.
With Quick Jesse's help, Barry was able to stop Magenta from crushing a hospital with a giant tanker. So it looks like there is gonna be a new speedster running around Central City for a while.