Oh, well, this is embarrassing ... it seems it's a different temple altogether.
Apparently there are
many temples named 法界寺 and it's not a unique name at all... the one in Kyoto just happens to be in a lot of tour guides and so be the one you find when you search the web.
Unfortunately you can't unsend an e-mail but they haven't responded yet so I guess I'll send them a quick apology and then try that town contact after all!
(I was so confused as to why she had been buried so far away from home, but now it makes much more sense.)