You don't have to be on the defense here. I'd call mommy dearest up and let her know how inappropriate it is to show up at your workplace asking for you and you have no desire to have a conversation with her. Let her know you will file harassment charges if she continues to show up at your place of employment. And then hang up. You don't have to entertain this woman, but you should stand up for yourself.
With how you describe her it sounds like she wants a sugar dad more than a boyfriend.
Given how transactional she seems to think of relationships I would ask her what her view is of how she should contribute to the relationship.
Men like this act nicely at first until they get too comfortable with you. She's only 23 so it makes perfect sense. She doesn't know much.
You don't have to be on the defense here. I'd call mommy dearest up and let her know how inappropriate it is to show up at your workplace asking for you and you have no desire to have a conversation with her. Let her know you will file harassment charges if she continues to show up at your place of employment. And then hang up. You don't have to entertain this woman, but you should stand up for yourself.