Mr. Lewis: The dc's for Sylvester and Mary Jane (2nd wife) indicate they are buried at Mount Hope Cemetery. The San Diego volunteer was not able to find a dc for 1st wife, Louisa. I would suggest that you either write or call Mount Hope and see what, if any, records they have on the Gilson's before making a final determination regarding their removal from Julian Cemetery list of burials.
I live in Stanislaus County, so can't help with on-site research. If you have access to the newspaper serving the Julian Twp. area see if you can find an obit for Louisa.

Mount Hope Cemetery
3761 Market Street
San Diego, CA 92012
(619) 527-3400
Pat - RAOGK volunteer