Could there be a possibility that GaGa might use dRugs just like any other artist do?

Yep.
Gaga said in an interview (I think it was the "60 Minutes" interview) that she smokes a lot of pot when she writes music and admitted that she also did cocaine some years back. And I remember that Boy George criticized her some time ago (maybe a year or so) because she said in an interview for a magazine that she did cocaine occasionally (at the time she did the interview)... I'm not really sure if she still did cocaine 1 or 2 years ago or if she still does.
I choose to trust Gaga when she says she only smokes pot but in the back of my mind I wonder if she does cocaine every once in a while, if she ever feels the need...

yes it is possible. she did admit that she was addicted to cocaine when she was younger.

Yes. A very big one

Maybe,but I still admire her so much