Not getting notified when certain friend text me.

So I don't get ANY notifications at all when My friend (Melissa) Text me. I go to my inbox and still nothing is there. The only way I can see her messages is if I go to her Contact Shortcut on my home screen and press the message icon. Then our whole conversation appears from days before. Why doesn't it show me when I get a text from her?! It's annoying that I constantly have to be manually checking if she has text me or not.