Eleanor was first mentioned in Deadpool (4th series) #9. Her appearance in #19 was a small flashback cameo. Her first full appearance was #30.
A future version of Ellie demonstrated a resurrection & rejuvenation healing factor. She heals and ages normally until suffering violent death. After that, her body regenerates itself back to full health and at the age her powers manifested, roughly her late teens. Whether Ellie-616 will manifest this ability is not confirmed.