There were dozens of churches calling theirself "reformed christian" so I am not sure which one you are talking about.
This is one of the major ones
Beliefs - Christian Reformed Church
If this is it, what you do is ask uncle to come over and discuss it with your mom. Or ask your mom what part of that religion does she not believe in
Next of course there are dozens of types of Baptist, which do not fully agree on the same teachings, so I do not know which type you are. Independent, Full Gospel, Reformed, United, Southern, Freewill are just a few of the many types of Baptist