Huh. That is super weird, and I haven't seen that before....anywhere. This seems like a pretty serious mutation and I would certainly keep my fingers crossed. If she's not able to push any further as a result of this 'fuse', it might be over for her.
The mutation, along with the stretch is a pretty tight spot to be in. I truly wish you luck on this girl and I don't give up! You never know. I would also agree with High roller that the stretch you're seeing is due to the light source being too far away. If your LED is 300W, I would look to hanging lamp 24-30 inches for veg. It will help stop the stretch, form tighter internodes and thicken all stems👍
I know this probably wasn't much help! Lol. But again, don't give up. Some tweaks and she could certainly grow through the mutation and move into heavy Veg. Cheers and good luck!😉👍