That question has factors that you haven't shared. If it were me - I would keep it. I am not in this for money, and I have no problem vegging a plant for 8 months playing around, flowering it for 10..12..14 weeks, and not worrying about how good it is til it's cured for 3 months. I have kept plants in the past (vegetables, herbs, and fruits too) that have had some horrible deficiencies. It's a good way to learn what these deficiencies look like, and how to remedy them. You will see that you can't just give it a huge dose of N because it's lacking in N..so it helps you to learn to curve on what you can and can't do. Also, it sounds like this is a clone of something you already have going. Why not practice on this as a sacrificial lamb rather than harming future sisters?
However if you do not have the time, space, or money to keep a sickly plant going, then you may want to chop it. Also, as plants die they attract pests. So if you do decide to nurse these little ladies, be sure to watch for pests, and keep the plant tidy-free of half dead leaves! Remember, you can not repair the damage that has been done, but what you can do is look for signs of new healthy growth. When you see this, continue doing what you have been doing to nurse it back, feed her moderately, and you can still produce a worthy yield. It is my opinion that getting yields from these plants is very VERY satisfying.