To be fair we only see her suggestion going as far as them snogging in his cabin (not that 60s TV would go much farther). It's Dr. Adams who pushes it into "You're madly in love with Helen, Captain. You'd lie, cheat, steal for her, sacrifice your career, your reputation."
It's still a weird thing to implant in your captain's mind while on duty investigating a serious thing.
She could have implanted that Kirk spilled a drink at the Christmas Party or thinks Klingons look better in pink
. Kirk asked for something "harmless" at first, then he asked for "something unusual, an unusual suggestion, something we can both be sure of". But no, instead, she can't resist the chance to live out a fantasy she must be obsessing with at the time. After all, Kirk is one uber hansom and sexy dude, right? Her fantasies clearly started in the transporter room and continued to that moment with the neural neutralizer (...and she's the best (probably the only) psychiatrist with penology experience on the ship.
)
Why
could she be "unprofessional" with her suggestion? I suppose age, inexperience and situation were factors. Noel was 24 years old (Marianna Hill's age the time of filming), fresh out of school (assuming a 8 year doctor program and starting at age 18) and probably on her first job assignment on a starship. Kirk didn't know her at the Christmas Party, their only previous encounter they both shared. That seemed not too long ago, so, I don't think she's been on the ship too long, perhaps a few months. In her brief time on the ship, she didn't experienced supernatural forces or near death and destruction yet, so, things are still "fun" to her. Then she is thrust into her first field mission under Captain Kirk himself no less. In addition, the mission is not supposed to be dangerous, rather everything is kind of fun hanging out with the Captain and meeting a galaxy famous doctor in her own field of study.
Maurice also has a good point that Dr. Adams intervened at this point. Adams must have lurking and listening outside the door for enough time to piece together a plan to control Kirk. I think he planned to fabricate the story that Helen recreated the same condition on herself as with Dr. Van Gelder, so she would need to stay at the Tantalus colony for care; all the while telling brainwashed Kirk that he will kill her if he didn't confirm the situation and leave Tantalus as if nothing is wrong. Then he would brainwash Helen that she wants to stay at Tantalus like the rest of his zombie patients. He would also force Kirk to return Dr. Van Gelder. Of course, unknown to him his plans would fail because wild card Spock was able to mind sift Van Gelder for the truth. If Kirk turned up without Helen and orders them to leave, red flags would be evident, and McCoy and Spock would confine Kirk and mind sift him for the truth.
In conclusion, is "the Noel suggestion of her romance with Kirk" the one thing I could change in TOS? No, this is just not that important compared to other more cringe worthy scenes and bad episodes that needed fixing. Plus, something like it was needed for the plot for Adams to come up with the plan to brainwash Kirk to be madly in love with Helen, so, Shatner can eat up the scenery in the neural neutralizer chair.
