Flirting signs are often hard to read. You never know if you should assume it’s flirting when it’s really not, but you don’t want to miss your chance by ignoring potential signs.
Girls will often take interest in your interests if they’re into you. You’re a Star Wars fan? She is too. You like baseball? She’s buying you guys tickets.
No, not necessarily for that, but in a society where women need to be cautious of who they invite over, especially when it’s the opposite gender, it’s a true sign that she trusts you if she extends an invitation.