The girl doesn’t bring up the fact that she has a boyfriend as soon as possible, believing that she was having nothing but a platonic conversation with the guy who instigated the conversation.
Girls are not always thinking about a guy’s ulterior motive in talking to them.
She is making conversation because that is what she does.
As a social person, she has no problem keeping a conversation going.
As the conversation ensues, she is not concerned about whether he is hitting on her, and she should probably tell him that she has a boyfriend.
When you ask the typical girl for her number, she has a sense that you are interested.
Should you ultimately use that number to call or text her and initiate the process of getting to know her, or ask her out on a date, her suspicions are confirmed.
Oftentimes, a girl wants to feel like she is actually liked by you and being pursued by you.
When you ask for her number, you are being assertive.