What's up with this girl?

So I asked this girl out at school last week(Wednesday) and she said yes and gave me her number. She seemed really into me and was really chatty and everything. Later that night I texted her about going out during the weekend. She said she already had plans. So the next day(Thursday) she barely said a word to me. I didn't go to school Friday so I texted her and asked her what I missed in cl and she didn't reply. Yesterday I sent her another text and once again no reply. What's going on????