It is not against the law to talk to a witness or even questions a witnesses statement. You cannot offer them anything of value or threaten any harm to them to get them to change their story, that is influencing a witness.
I think there must be more to it than that, why woudl your friend plea out just for a discussion. IF you were told to stay away from the victim and you didn't that is a problem, but if you were honestly asking questions you did not know the answers to and there was not issue of you knowing she was a victim and no restraining or stay away orders you should be fine. You should work with a local attorney if it goes to court.
Your question is an odd one since you have already been charged with a crime if a warrant was issued for your arrest. If you mean can you be convicted, then that is an entirely different question. Your charge sounds like it may be a felony which means that you can serve time in prison if you are convicted. You should hire a lawyer immediately or ask the court to appoint a lawyer to assist you in your defense. Best of luck to you.