What should I do?

We started our friendship through online games honestly I'm having fun with her however few years after our friendship became more deeper. She shares her personal problems and seek some advice from me from smaller to bigger.

However aside from all happines and closeness I suddenly feel alone when I talk to her. Actually in a few years we been friends she is the one who chatted first, or she is the one who started the converstation because when I chatted her she just ignore my messages. I actually don't mind it before but now.. I don't know. Why? She only chatted me when she has a problem or rants I actually don't hate it since its also make me special for her however when she finished talking or ranting fron her problem suddenly she will find a reason to stop our conversation like (She have to sleep early, Eat, and Go somewhere) it feels like shes making excusses.

Honestly, I have this feeling right now that I been used only. When we talk I have to respond my best answer to his question and give her best advices however after that I feel empty.

I see her as my friend but at the same time I feel like I'm just a stranger to her.