Most Helpful Girl
Call her and ask to meet up. You can keep calling if she doesn't pick up or you can get the hint and either text her or leave a voicemail saying you'd like to meet. Talks like the one the both of you need to have needs to be done in person. Three months is a fairly long time to realize you made a rash decision and want to be on better terms... in girl world at least so she may not want you back and you'll have to deal with this fact. Realize that not getting her back (friend or lover) is a possibility and accept it. Unless you truly believe that by talking to each other you will either be able to mend, or put whatever happened behind you- it may just lead to more anger and resentment.
Most Helpful Guy
I'm Going To Give You My Professional Unlicensed Opinion, Speak From The Heart, Be Gentle & Sweet. If She Is Cold Or Ignores You Then It's Over & You Have To Accept It. If She Is Responsive Then Continue Talking To Her...