Why do girls do this?

TLDR; girl I was talking to online removed me for no reason, and I don't know why she did it

I met a girl online on this app, on Wednesday. She had commented on a question I had asked once in my local language, and I immediate realized her to be from the same country I was, so we took it to the DMs and hit it off. She gave me her Snapchat and told me she'll be talking to me from there from now on as she was deactivating her G@G account, so we exchanged IDs.

We were mostly just talking and casual flirting, and her responses to all my advances were very positive. She was much more talkative than I was and it genuinely felt like she was actually interested in me and that things may go somewhere if all goes well. I learned that we had a lot in common and that she also lived in my city, just a couple minutes away from where I live.

We'd mostly talk at night because she'd said she had a night job and she'd get free by 12AM. I was mostly awake during the time and I have work to do of my own, so it was fine by me. Last night, I hopped on Snapchat as usual and I saw she had seen my snap but not responded to it. Then I clicked our chat open and saw that she had removed me as a friend.

I really don't understand what happened and why she'd do something like this for no reason. On the night before yesterday, everything was going so smoothly. We talked till 3:30 and we wished each other a good night and went to bed, so this doesn't make any sense why she'd do something like that. Am I missing something? I would appreciate every single helpful response under here.
Why do girls do this?
She's not interested in you like that, was bored and passing time
She's doing it to see if you'll chase after her
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Updates
9 mo
GUYS!! So she added me back on Snapchat just a couple minutes ago. I asked her what's up and she apologized profusely, saying she was getting rid of some unnecessary friends the other day, people she didn't talk to/wanna associate with anymore and accidentally deleted me too. Then she reinstalled G@G again, went through our old DMs, found me again and re-added me, so I guess that's that?
Why do girls do this?
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