She picks the name Ms. Marvel because she’s a big fan of Captain Marvel, whose original superhero monicker was Ms. Marvel.
(In the MCU, there is no Ms. Marvel to inspire Kamala to take that name.
In the Ms. Marvel comics, Kamala got her powers by coming into contact with this substance called the Terrigen Mists, which is what gives Inhumans (like Black Bolt, Medusa, etc.) their powers.
What we will learn about where those powers come from, and how they come about, is specific to the MCU.