Why do some girls show interest in you alot at first then when you guys start texting and you show..?

some interest back she ignores and acts like you dont matter? This hasnt happend to me yet, but i want to prevent it as much as possible. What does the guy do to make you ignore him, besides playing hard to get. Is it him showing to much interest and creeping you out in someway? Or something cheesy he said? or what