A couple of things.
On the topic of whether or not she would be able to see spiritual beings like stands, thats probably a yes. Her soul magic in particular would require this but even outside of that, spoilers for Project Horizons,
right before her original body was completely erased from existence, she physically interacted with the souls of her deceased loved ones such as P-21, Morning Glory, and her mom, who were now free to move on to the afterlife.
As for her massive upscaling, she downscales from
Legate, who can casually bust apart
Alicorn shields in single strikes, which in turn scale to things that would normally one shot Alicorns themselves physically, who should be superior to the nerdy less physically inclined
Littlepip.
As implied Legate did not take these supposed terrors of the wasteland known as Alicorns seriously at all, and even laughed at the Alicorns sent to attack him. Blackjack however was serious business, and she held up far better in physical combat.
Going to comment on Social Influencing because it seems like something Jose is inclined to attempt. Given the intent is to kill, I doubt Jose is going to be able to talk Blackjack out of fighting, especially if it comes later in the fight. One of the main points of Speak as a story early on is how its a character study and a reflection thereof from an outsiders perspective, but in a similar ****** up vein as Neon Genesis Evangelion was a study of mecha pilots. Point is Blackjack is on a whole other league of mentally "not okay". There are therapists with knowledge of Blackjack's entire backstory after she came to the surface, who could see physical manifestations of her emotions, that attempted to treat her, only for the roles to reverse. The only thing I could think of that would give Blackjack pause during a fight was if her opponent was either a child, or significantly attractive.
Blackjack tries to end fights as quickly as possible. Her preferred tactic is to manifest a sword she can use once she overwhelms her opponent with teleports.