Man, the queen really was horrible. She had visions about how Pryde would be a terrible queen. And what did she decide to do? To completly neglect her by then 4-6 years old for 8 entire years. To the point that Pryde didn't even knew she had a little sister.
The Pryde right now already knew about Tiara beacuse her past life memories, but can you imagine the shock that the original Pryde had to suffer? "Pryde, you have a little sister we hadn't talked to you about and who your mother has been fawning over while completely ignoring you". Then everyone keeps talking about how beautiful and kind Tiara is, and how much she ressembles the queen. No wonder Pryde felt jealous, she was being objectively discriminated against