Is there a nice way to tell your friend when she's acting a bit slutty??? Should I say anything at all?
Depends on how you define "slutty" and how your friend's behaviours might effect you and your friend. People do have a choice in their life to do what they want, as long as it doesn't bother others. If you feel like you really have to say something, say it straight to her, might not be the nicest way, but it is direct, and give her a clear sense of what you meant. Careful with words of course, so don't say "you are a slut", say "you need to pay attention more to who you sleep with" or something. I don't know the full story, so I can only guess.
Whether you say anything depends on whether her behavior is hurting her or anyone else. If it isn't, I'd say that she's free to do what she wants. But if it's out of character for her, you could always bring it up that way- "You haven't been acting like yourself lately." And then if she asks what you mean, describe what she's been doing. Name calling isn't going to get you very far.
Normally, I wouldn't care. Everyone is entitled to a skank phase if they want. I don't care lol. The thing is... her boyfriend is deploying tomorrow. He's in KY and soon to be in Afghanistan. She still sleeps at her ex's and she was all over another guy last night when we went out. I hate the idea of cheating, especially on a solder who's about to go away for a long time. She's not sleeping with all three (just two), and maybe "sluttly" was not the best word choice, but I almost can't stand being around her like this anymore. It's bad and it isn't really like her. I don't know if I can continue to "ignore it" for much longer... and I don't know how to talk to her about it.