Hi, I have very short experience of talking and texting to girls.
So apparently, this girl would reply back to be for several times
but she'd stop replying to me. She's done this more than once, and she never have
re-initiated the convo. So I stopped texting her and talking to her for two days.

I have been thinking about how am I supposed to come back if she either as in person or through text asks such:
"Why don't you talk to me anymore?"
"Are you ignoring me?"
"Hi, I haven't spoken to you lately"
of sort.

Thank you guys!

You are either texting her too much or she thinks your a boring texter. I don't text unless its to set something up in a couple of days as I got a lot more confidence in my face to face game. If you do text her again(you shouldn't, you need to let her be the first to make contact) act like your not disappointed that she didn't text you back, so I wouldn't text her any of those examples you put. She needs to know that she's not the center of your world and when she didn't text back you didn't care. Another thing is to game more girls you need to have more options so when this chick doesn't text you back you won't care enough to make a thread about it.

Thanks a lot, that really helps!