What's the behavior you don't like? Did she screw your best friend or does she leave dirty plates on the table?
Your response and actions are on a spectrum depending on many things.
First, if you're in a LTR, consider you already have a lot of time and energy invested so unless you're looking for a way out, dumping someone without giving them fair warning is just plain dumb. Not to pick on you OP, but your post kind of reminded me just how little value people see in LTRs and marriage these days that they're willing to crumple them up and throw them away like a used McDonald's bag at the first sign of trouble or over trivial small s*hit.
You'll get varying answers and I am a fan of S&D in some cases but if someone is doing something I don't like to the point of where it's affecting the relationship (and keep in mind YOU likely do s*hit to piss her off too so no one is perfect) I tell them about it; why it pisses me off and why it's bad for the LTR. Going silent in a LTR or marriage doesn't address the main problem or solve anything and is for the most part a feminine tactic. I think I'm more assertive, maybe even too aggressive, than most on this site so I always believe in taking the lion head-on. BUT, be firm and masculine about it, not an over-emotional ranting d*ick. How would James Bond reprimand his LTR chick? He'd be cool, firm, confident, and state what is pissing him off and leave it at that. Then he'd hop in his Aston Martin and have a martini with his hot chick "friend" who's 25 years younger, lol. Do similar.
Give her an opportunity to correct the behavior. If it keeps happening after you've said something, like she doesn't give a s*hit about what you say, then it's time to call a timeout. YOU must call it. Two weeks is the average. If this doesn't resolve things, THEN it may be time to end the relationship and move on. EVERY relationship/LTR has a half-life with the average being 2-5 years. Marriage has divorce peaks at 3 and 8 years. You'll know when time is up.
Good luck.
~Dash~