I thought there was a thing mentioned where the brainwashing wasn't even really that and instead just unlocked her love for yuri or something?
Semantics?

Riri has almost no compunctions against altering human minds. Riri brain washed away most of Mom's hangups and restraint so Mom would be conveniently useful. At best, it's unclear how much was a healthy intervention and how much is reeducation to the fetish and fresh personality Riri needs. The love for yuri should be natural, but it's still brainwashing.
Which is darkly funny. Riri's blue and orange morality at least spreads yuri.
Going beyond that and taking it seriously would be less funny, but it's still alien infiltrator brainwashing and not medical care.