If a girl calls to say hi, does that means she's interested?

Is she a member of a cult? If so, she could be trying to recruit you.

Have these dinners been with just the two of you or are others involved? You didn't provide a lot of info, your ages, are you both in school or work in the same industry? She might be trying to broaden her circle of friends or maybe she finds you interesting. If you don't find her interesting, limit your contact.

Yes, everytime we have dinner. It's just the two of us. I am in my late twenties and she's in her early thirties. She's working but recently I lost my job. We are in completely different industries.

She's completely secular and I've known her for half a year. We've only become to contact each other more frequently recently.

No.