Should i txt or do this in person?

Theres this girl ive been sorta seeing unofficially as she borke up with her ex of 4 yrs about 3months ago and didnt want to get into a relationship too quickly , so i gave her time, and now we're doing all the dating stuff, however i feel she is too selfish about her own feelings, and ive been there for her 100% of the time, and made myself look easy, by cutting all the games.. she seems to be playin, and leading on another guy, but claims she isnt to blame, but he isnt getting her signals.. So i want to sms her right now, cause im pissed and dont wanna get too involved any more, should i sms, or tell her in person.. " I feel you only care about ur own feelings, and I see I'm not important to you, I don't think we should speak anymore, its best for everyone involved, hope whoever you like makes you happy.", i wanna make her feel bad, as i know she'd find it hard to accept. i really am over it all, and dont care if this ends it all..