Thanks for the pictures. I wouldn't give up on her. I think you can get a crop.
Those look a lot like mine did. I'm sure the problem I had was too much light. I had power meters on my lights, so I know precisely how much power the lights were drawing. (I had two 240-watt XS2000s in my 2x4 tent.) While in late vegetation, each light was as high as 140 watts and the plants only showed slight leaf tip burn. I didn't know it was light stress at the time, though. Otherwise, the plants looked healthy. When I flipped, however, the light burn worsened in a hurry. That's when I started a thread about it. We tried several things, but what worked best was to lower the light power. By the time I harvested, each light was only drawing 60 watts--less than half of the power setting during late vegetation.
I know that's contrary to popular wisdom about using high intensity light level during flower, but turning down the power was the solution. I do recall one of the more experienced growers here (I don't recall who) saying they turned down their LED lights at flowering time. That stayed in my head as we were working on the solution. So, I suggest reducing the light power.
Light stress or burn is hard to diagnose because it looks so much like other problems, but if everything else has been tried, try reducing the power.
So, your leaves look a lot like mine did: Tip burn and edge burn up the leaves from the tip. I tried to find a good example from my image collection. Here's one:
View attachment 1342946
I apologize for the long post.
