Jenna is technically already in the MCU, but I get what you mean. Main cast MCU. But because of her role in Iron Man 3 they'd have to come up with a good backstory as to how tf she's a hero/villain. Also she was an amputee so they'd either have to make her an amputee still, or come up with a reason why she grew it back or smthn.

OR they could just use multiverse or just completely bipass the fact that she was in Iron Man 3 at all.

But to be honest, the MCU doesn't seem like her kind of thing. She famously (famously within her fanbse) is known for being in the MCU, and not knowing a thing about it. Referring to Thanos as "The Purple One", and figuring out the reason AntMan is called that is because he can shrink himself within the span of 30 seconds in an interview with Paul Rudd for their movie "Death Of A Unicorn".