Ex girlfriend is hard to understand

My ex and I were together for 6 years. She has bad mood swings and really bad with money. She is also disabled and a horrendous flirt. We out of nowhere broke up and she moved in with her mother. About a month passes and we start talking and sleeping together again. She has all kinds of pretty words to say and talks about no matter how hard she tries she can't walk away or fathom sleeping with someone else.

This goes on for about a month and then this past Monday she is quiet again and claims that she has hit a reclusive mood again. I am suspicious but roll with it till last night (Wednesday) in which she makes a rather seductive post on twitter about an unnamed individual. So because I am a glutton I hack her facebook and in the same night she has a long sexting string with a guy she went to high school with. I confront her about the twitter. I simply state that we are not together but if she has interest in another I would like to know. She denies it saying it's all a piece of fan fiction she's writing. She doesn't know I know about the sexting.

We talk for awhile and it's ultimately decided we no longer speak. A couple hours later she texts me wanting me to buy the youngest a pair of shorts for gym class because she has no income. Of course I tell her no. I love the kids (I really do) but I can't be taken advantage of. So now I don't know what to do. The other guy from looking at his profile has nothing in common with her rather eccentric tastes but they are planning a meeting at his house. She also says she's emotionally blocked and is doing anything to try to feel again. I know it's only a matter of time before she texts me and I don't know how to not respond. Same time I'm worried she does it because I'm safe and familiar as well as dependable. She also says her mood swing is because of the waning moon.

She claims she's not talking to me right now because the things she has on her mind are issues she doesn't connect with me about. The very idea of her sleeping with another both enrages and saddens me and I don't know how to deal. Should I tell her I know about the other guy? Any advice?

I don't think that anyone needs this emotional roller coaster. Its not fair to you. If she texts again, don't respond.. Hacking her twitter account shows that there are trust issues. Let her move on so that you can too :) Trust me, your going to go nuts trying to figure this one out.

Oh yes major trust issues. I used to be married to a woman who cheated on me twice. I was in a good place when the ex and I got together till she started all her flip flop business a couple years back. Now all this business since we split made it all the worse.

If I'm honest I don't know if I'm strong enough to not respond to her. I'm having an extremely difficult time not texting her first.

Well my friend... Do you want to be with someone you don't trust? Think about it..
If you constantly respond, or text her first she'll know that you will always be there. ALWAYS. How bout getting a new phone number ? Stopping all the contact might be a solution and what you need to get her out of your head.
I know it's hard to do.. and I can easily say to you to leave because I can say it and I've been there and I would never tolerate it. Don't play the game my friend. Give yourself a chance to move and live on.