She will be able to live like this forever, easily. She has rental income from her cottage, she doesn’t pay rent or pay bills to her parents, and she earns money from YouTube. She literally has zero expenses, no food shop, no car. All her holidays are family holidays paid for by her parents (who own at least two properties).
Tbh, I would imagine Ruby’s actually saving a lot of money, even if she’s not making millions. She was able to afford a mortgage at 18 with her parents as a guarantor! She’s in a very lucky position.
The reason why so many authors, actors etc come from affluent backgrounds is because they’re given the luxury of having no expenses and not having to work in their 20s so they have time to chase the dream. These types of people will always land on their feet because they have that familial support.
If she continues getting sponsorships and producing content she can continue living as she does now for as long as she wants to. As long as her parents are willing to have her in the house, that is. And it doesn’t seem like they’re too bothered about her being there.