A warlock/sorcerer blend is what she wants... but given the... uh... sociopathic bent of your players, are you sure she'll be even comfortable gaming with them? Seems her idea is nothing like what the other players are into. I feel there's no point in making her a special snowflake if she's going to hog the spotlight, and based on your description of your players, they're likely going to try and 'do' her. (Sorry Eric's Grandma!)
The main 'issue' with modelling superheroes with 5e is that 5e's design deliberately steers away from high-powered gaming. Were this 4e, you might have more luck - it's 100% designed with big powers and combat taking the fore.
I don't know man... your whole side of the conversation makes me real nervous for your lady pal.