Carys lies about everything but I believe her anxiety is very real. This woman created her own isolated, safe bubble where walking around the house doing nothing counts as a fulltime job, where everyone loves her and where even the slightest criticism gets either ignored or, more often, deleted. She surrounds herself with people who kiss her ass and spends her entire life either in her house or online on the gram. It's all very safe, very repetitive, and probably very toxic.
When she goes out and does stuff on her own, she's no longer in her little bubble where everything is about her. No longer 'omg I love you boo' and 'you are enough' and 'you're such an inspiration Carys'. Just real people with real jobs and real struggles who couldn't care less about her. She doesn't know the real world, so of course it terrifies her.