1) it’s some kind of ~probe and that’s worrying enough itself (something dark taking notice ain’t ever supposed to mean good things) 

2) it’s a mind-probe - Leia doesn’t seem to feel it that way? but Ben may

2a) It just probes. Creepy, worrying, invasive, but still far from brainwashing

2b) The Force is mysterious etc it just somehow... changes something? That’s not brainwashing. Horrible but not the way brainwashing works. At least with brainwashing you can try to resist or manage to break out if it, this is worse. 

3) whatever it is, it’s interested and here to stay and

3a) it comes back regularly. 

see 2a) and 2b)

3b) it actually stays in Ben’s head all the time and i don’t think there’s a word for that. i don’t know how the Force works, but Force Bonds between Masters and Padawans do exist, so i’d see it more as forcing the bond on someone and using it to manipulate them. indoctrination? grooming? how much influence would it have?