Is it a good way to end a relationship randomly. I don't want to say it to my girlfriends face because she's help me deal with depression and she's encourage me to stop using drugs. In genreal she's done a lot for me and I'd feel really bad to randomly break up with her face to face so I want to do it through a instagram messege and block her so I don't have to see her reply.

No, that way has no honor, it's a cowards way out, as she was good to you, you must be good to her and show the respect and strength it takes to gently tell her the truth as you look into her eyes 

whisper it in her ears.

Ahahaha that made me laugh. 

Breaking up by text like Rab said is the cowards way out. Shes shown you a tremendous amount of respect and care, if you want to show her the same amount of respect and caring back, you need to man up and do it in person,regardless how it makes you feel. In person is the right thing to do.

Never get a girlfriend in the first place. Problem solved.

Oh god no. Certainly not based on your short summary of the relationship you've had with her. Honestly, and please don't be offended, I'm kinda worried how you'll tackle this if you're entertaining the idea of brushing her off via a text/block combo. Try to be as kind as possible.

Sounds like she deserves to hear it in person.

No, that's quite horrible way to end a relationship. I'd say talk to her, be honest and give her reasons as to why you're breaking up, whether it's something about her or it's something that's got only to do with you.

My girlfriend broke up with me through text. Worst following six months of my life. I'm still pretty young but still.