Does it still look like Kershill?
On first looking I would say the answer is no.
The typical C16th
K will have two loops (one on top of the other) to the right of the main ascender, as we clearly see in
Kershill and
Katherine from the first image. It is also commonly the same form in both upper and lower case use.
This letter doesn't appear to have two loops. It looks like
B. It also looks very like the (explicitly lower-case)
b in two examples of
february in this clip.
Furthermore, I think we have
in park myll in the second last line of this clip, where the
k doesn't look like the first letter of Janet's placename.
On the other hand, if Janet's surname is
Bruce, the
B doesn't look much like the first letter of her placename. It's to be regretted that a smudge has affected this part of the page.
I'd like to see the full page for the marriage record if you can post it, just in case.