Comparison is the only form of logic this fandom apparently understands.
‘Nesta was self-sabotaging and she needed to be imprisoned.’
Feyre wasn’t eating or sleeping well to be in a fit form to encounter any creature she came across. But she wanted to partake in dangerous missions when she couldn’t handle seeing blood or anything even resembling it. Those are suicidal behaviours.
Feyre’s imprisonment was for her good, right?
‘Nesta was a threat to the people and had to be contained.’
Feyre was barely adjusting to her new fae body, let alone have complete control of her magical abilities especially when her emotions are haywire. She proved this to be true even months after she “healed" during the High Lords meeting. Feyre begged to be taken along on patrol duty along with the sentries who had no power or means to protect themselves from her outbursts, and she threw temper tantrums when Tamlin tried to reason with her.
Feyre was a bigger threat, right?
‘Nesta didn’t contribute to the court.’
Nesta didn’t have to. She was only a subject in the court, who already did a favour to Night Court and all of Prythian during the war.
Feyre was going to marry a High Lord. All she was asked to do was play the role of Lady of Spring and socialise with her peers and familiarise with the court matters. She couldn’t have one conversation with them without looking down on the people or their traditions. She wouldn’t learn anything about the court without griping about how boring it was.
Feyre was living off Tamlin without doing anything in return, right?
In Nesta’s case, it was abuse and unfair. Feyre (Rhysand and IC) forcefully dragged her back and imprisoned her when Nesta wanted a life far away from them. If she was being such a bother, Feyre could have just cut her off and let her come to her senses on her own, maybe have a suicide watch keeping their distance from her in case it was a genuine concern.
In Feyre’s case, there was no other way to stop her from running out of the manor without protection, running into dangers headfirst which she threatened Tamlin with. If anything, locking Feyre up doesn't essentially qualify as an abuse when she openly exhibited all signs of putting herself and others in danger, and it was called for.