There are small claims procedures in Scotland (not separate courts) but this seems a bit more serious - really she needs to stop the neighbour doing more of the same, not settle a one-off damages issue. (A new rowan tree a few feet high might be 20 or 30 quid, not worth hassling over). That is why a lawyer might be an idea. "Neighbour from hell" cases require more than simple procedure-following to deal with.

Evidence in Scots law is different from England or the US. You need corroboration of every item of evidence used in court. There is no relaxation of evidential standards just because the case is over a small amount.

I would be inclined to forget about the courts and look at the planning issues around that extension. If the guy's damaging her property in its construction, she probably has grounds for getting it refused and maybe even requiring demolition of what's already been done.