Tell her "We only had 4 dates in 4 months...that's like seeing eachother once a month... Tell her that it can't continue being like this... Usually when people date they see eachother more often...it's just not working out with us... Tell her in person... But be sure to tell her u hade fun... Let's just be friends... And tell her that in person... She won't hate u
Just tell her point blank that you want to break up cause of what ever reason it may be.To break up on sms is a bad idea cause that way you never really do break up just keep on hanging. So i suggest call her up meet her and break up.
If your worried about hurting her feelings...you could simply be honest(on phone)&tell her it's just not working out for you.If you do person to person(I think that hurts much worse)But phone is still personal,yet not as confrontational when it comes to possibly hurting someones feelings.Just my opinion.Do what you feel is best.But don't prolong it or it will be much harder..