Ravenna, also known as the Evil Queen, is the selfish and tyrant ruler of Britain, who learns that her stepdaughter, Snow White, is destined to surpass her as the "Fairest One of All". However, upon learning that the only way to remain in power is by consuming Snow White's heart, Ravenna recruits a Huntsman to capture and kill the young princess in exchange she tells him that she can bring his wife back from the dead, which is a lie.
Ravenna's name comes from the name Raven, meaning "death" or "doom".
Even though she says she has lived 20 lives she retains a naive and childish personality meaning her magic of immortality completely stunts her mind and body.(since many people died at the average age of 40 and she said she lived 20 lives, we can presume she is 800' or close to a millenium. It just depends on what she considers a whole life)
We can presume she only learned to use the power of stealing young women's lives later on in her late 20's and that is why she has only ever stayed at that age.
Like most evil step mothers she has powerful magic akin to many Grimm brother fairytales.
When in the woods as William she says to Snow White that "she was the only one who could stop her, the only one who could save her" so possibly there is a glint of humanity still in her (meaning that she knows of her misdeeds and she knows she will continue to destroy kingdoms as long as shes alive) this is also seen when she mourns her mother and brother.
Differences between the disney evil queen and Ravenna is that:
• The evil queen only fears not being the fairest "looking" in all the land, whilst Ravenna only fears "death"
• Ravenna has a wider family and richer history spanning years, whilst the evil queen is alone.
• Ravenna's powers surpass the evil queens, Ravenna can shapeshift into both people and animals, she can keep other people immortal such as her brother, steal life, conjure army of quartz and monsters of quartz, can't die by non fair hearts "royal blood", withstand elements like fire.
Despite her powers and that she's more powerful than everyone else a monster could easily stop her such as a dragon.