No, Lorna Bucket is not the regeneration of Jenny.
Lorna's first encounter with the Doctor was detailed in Lorna's Escape, a short story in The Official Doctor Who Annual 2013.
The story specifically indicates that her first encounter with the Doctor was when she was a child.
It also indicates that she lived with her father (although this could be an adoptive father), and describes the Doctor from Lorna's perspective as "mysterious traveler and his strange wooden box".
Based on the information in that short story, it seems unlikely that Jenny == Lorna.
Also, Jenny was "made" on the planet Messaline. I can find no indication that the Gamma Forests were associated with Messaline.