I'm guessing her SW used the word forever quite a bit, referring to a forever family, because it was it was certainly part of her vocabulary when she came to us. When she first started playing hairdressers and doing my hair on a daily basis, she'd pretend I was also a customer coming for a sleepover. "Are you staying forever?" she'd ask. Or she (the pretend hairdresser) might be going on holiday and coming to stay with me. "Can I stay forever?" she'd ask.
We still play hairdressers but she no longer asks her customers if they are staying forever, or asks if she can stay with them forever. Perhaps this is a sign it's sunk in that we really are her forever family.