What does it mean if a girl keeps the text conversation going (and replies fast), but never texts first?

-I started texting my crush on Monday. Most of the time, she started typing her responses as soon as she saw them (which in this case was almost always... within 1 minute). Her responses are not kinda big (they aren't novels, but they aren't 1 or 2 words responses). Also, there were times when I responded like... 15-20 minutes later, and she was still replying to me in like 1 or 2 minutes.

-She barely uses emojis, but she uses lots of exclamation points

-Yesterday, I texted her for the 2nd time. We were talking about a movie we both liked. I asked her what her favorite scene is. She told me which one it was. I didn't know what to reply, because she didn't ask me the same question back. So I tried to figure out a way to switch to another topic, but I wasn't able to. 15 minutes later, I still hadn't responded to her message (I was still thinking about what I should reply), and she asked me "What is your favorite scene?". Considering that I hadn't responded yet (even though it showed that I saw her message), I think it might be a good sign that she went back to me and asked me that. I think it might be a sign that she was actually interested in having a conversation with me, or else she wouldn't have attempted this.

-She often says things like "I agree with you", etc.

-She ends the conversation by saying that she's feeling sleepy, and that she's going to bed. She did that both times I talked to her, but everytime she said that, it seems like she actually wasn't lying because she didn't go online after that (well, she stayed for like 3 or 4 more minutes, but then after that she officially left for the rest of the night).

-On the first time, when we ended the conversation, I told her that I enjoyed talking to her (she responded by saying that she also did). Last time, when the conversation ended, she was the first one to say it.
Updates
+1 y
Sometimes, when I'm typing a message (which often takes me a few minutes), she opens the conversation, and then leaves after a few seconds (there's an icon that shows if the contact is looking at the conversation). And like, she doesn't even need to click on it to know if I'm typing or not (we're using facebook/messenger, so she could know if I'm typing just by looking at the list of all of her text conversations). I think this might be a sign that she likes me and wants to keep talking with me.
Updates
+1 y
When I say that she uses a lot exclamation points, I meant that most of her sentences ends with a "!". I was not saying that she is ending her sentences with like "!!!".

I'm sorry if this was confusing!
What does it mean if a girl keeps the text conversation going (and replies fast), but never texts first?
Post Opinion