What's the gentlest way to break up with a girl?

My rant, if you wanna hear why:

She's always talking about other guys and how great they are, idolizing male celebrities, and bringing up all her exes.
She'll also sometimes send me a text that doesn't relate to what we're talking about, then say "Didn't mean to send that!".
She told me goodnight at 11 last night, and come to find out she was up till 2:30. That and the fact that she sent me the wrong text shortly before saying goodnight, tells me she was up so late talking to someone else.

I don't have any proof of wrong doing, but I don't like the way she talks about other guys and I'm highly suspicious she's talking to them too. So I'm done, but I also want to let her down easy.
Updates
11 mo
This should be in "Break up and Divorce", but it didn't give me the option lol
What's the gentlest way to break up with a girl?
Post Opinion