What did you done girls, when your crush started to like you?

I'm a 24M and she's 21F. For about 5–6 years, since school days we've seen each other around fairly regularly, but we've never actually had a conversation - I didn't interest her these days. From these days I noticed a lot of eye contact from her, and I often felt there was some mutual attraction. Even her body language toward me seemed she likes me.

Things chaged drastically, I started to like her. A few days ago I finally approached her and told her that I liked her. I asked for her number and handed her my phone. She smiled, thought about it for a few seconds, and then typed her number into my phone.(From these days still I got her eye-contact and body language suggested she is into me)

A few minutes later I sent her a simple "Hi" message, but I didn't get a reply.

After two days, I met her again and asked whether she had accidentally mistyped her number. She said she hadn't been online and that she was "thinking about it." She didn't seem uncomfortable, awkward, or surprised that I brought it up. She was calm and smiled during the conversation.

1. What confuses me is that if she wasn't interested, why give me her number in the first place? On the other hand, if she is interested, why not reply to a simple message?

2. From an outside perspective, does this sound like someone who is interested but unsure, or am I reading too much into the situation?

I'd appreciate honest opinions, especially from people who've been in a similar situation.