Sorry to hear that she has passed, David, but that is a nice way to remember her. You probably might want to start by contacting the American Camellia Society:

https://www.americancamellias.com

If you have a newly developed camellia, they would be able to assist in the process. If you do not have one, hybridizers and camellia enthusiasts who have new introductions might name them for your mother-in-law but you would have to discuss this with them first. But as the registrar of names, ACS might be able to facilitate things. Below is a link in which the ACS reports names newly registered and more importantly, the name of the person/company/etc.

https://www.americancamellias.com/care-culture-resources/camellia-cultivars-registered-by-the-acs

Additional info:

https://www.americancamellias.com/care-culture-resources/developing-new-camellias

Note that some areas of the website is for ACS Members. I got to these pages without entering any userids or passwords so I guess anyone can get to them.