I don't think we fully comprehend how perfect Parker is for the role of Mastermind. In the Pilot, every one of them notices how good Nate is at his job and comments on it but it's more like light teasing 'admit it you had fun' or the more nudging 'did y'all notice how we totally rocked it as a team last night'.
But PARKER is the only one who notices and comments differently. Parker asks how he knows the number of guards and when he says to note the haircuts she doesn't throw a fit or pretend to just gloss over it. She notes that he noticed that while it escaped her eyes. She's the one who says things like 'here's the thing, I'm really good at this one thing but you- you can see the whole plan.'
Parker is the one who jumps in on the planning the most aside from Sophie. She takes note of everything like it's a safe to be cracked - she's careful, methodical, precise, but has fun with it her own way. Parker is the first of them to venture of for a job on her own to save someone she loves. And at the end of the episode she's the one calling the play because Nate trusts her judgement, which I must say is a rare case considering how much he relishes having control in the con (which would be another text post essay I guess)
Parker's also the only one who had a solo episode focusing on how to combine all the roles. She did the Broken Wing Job stunningly, and I think that's where the seeds of her shift of roles turn into a full fledged sapling.
Also Parker and Nate both have this very old school meets chaos meets emotional detachment fuelled scariness when it comes to cons. It's not what makes them great masterminds but it's what makes them interesting ones. And like we see in Redemption, Parker's evolved to a point in leverage co where she can read into the job like a safe with only a hatchbolt as a lock and walk off just like Nate did. I know people consider Hardison Nate's surrogate child but to me it seems Parker has always been kinda his legacy.