Evelyn's family would not tolerate her having another lover so she could not use money from her them for such a purpose. Thus, she could only use her jewelry. And the ones from Chester at that since her family would notice if something they gave her went missing.
At least, that was what Chester hypothesized.
But Evelyn did not do any of it. She never even thought of cheating even though her husband did it almost on a daily basis.
Yet, Chester kept insisting she was cheating on him even though he was the one doing it to her.
When Evelyn got pregnant, Chester fully believed she had it with another man. And since he thought it wasn't his, he asked Evelyn to abort it.
Evelyn refused. It was their child. Chester was her first and the only man she had slept with.
She didn't like Chester, but she felt bad for the child. Likewise, she couldn't really abort a child with royal blood, and a child of the king at that, even if it was Chester himself asking for an abortion.