Ok, I'll start at the beginning.
Problem number one: You are far too open with this girl, and she is abusing it. Now you have a couple options, you can either a) Take some time to yourself, accept what has happened, *insert inner peace stuff here*; b)get petty revenge by attacking her verbally and emotionally (but do it in a cold and brutal fashion, don't get teary-eyed or anything otherwise it will not work) NOTE: only do this if it makes you feel better, because getting you back on your feet is the biggest thing right now; c) Create an emotional block to stop yourself being overwhelmed and deal with it a little at a time until it doesn't hurt so much.
Problem number two: She knows how to get inside your head. Now, your best option here is to focus yourself on your goal (the topic of your conversation/to answer a maths question/etc) so that she can no longer make you feel bad about yourself when she is in the wrong. So what you need to do is ignore pretty much every attempt she makes at controlling a conversation and be persistent about what you want to say, and when you are done, just tell her to 'shut up because the conversation is finished' and walk away, head held high.
Problem number 3: You are still emotionally attached to this girl. My advice, throw yourself into anything and everything which makes you happy, as her seeing you happy without her will throw her off her game and she won't be able to pull the same old tricks on you again. Another thing you should do is to always be around one or more of your friends, so when you see her, you can look to your friend and start a conversation, which will make her feel as though you are over her which will do exactly the same thing as being happy will.
NOTE: I truly think that making her feel bad will not help, BUT if you can honestly say to yourself that it will, and you know her well enough to pull it off, then that is your decision and I hope it makes you feel better.
Problem number one: You are far too open with this girl, and she is abusing it. Now you have a couple options, you can either a) Take some time to yourself, accept what has happened, *insert inner peace stuff here*; b)get petty revenge by attacking her verbally and emotionally (but do it in a cold and brutal fashion, don't get teary-eyed or anything otherwise it will not work) NOTE: only do this if it makes you feel better, because getting you back on your feet is the biggest thing right now; c) Create an emotional block to stop yourself being overwhelmed and deal with it a little at a time until it doesn't hurt so much.
Problem number two: She knows how to get inside your head. Now, your best option here is to focus yourself on your goal (the topic of your conversation/to answer a maths question/etc) so that she can no longer make you feel bad about yourself when she is in the wrong. So what you need to do is ignore pretty much every attempt she makes at controlling a conversation and be persistent about what you want to say, and when you are done, just tell her to 'shut up because the conversation is finished' and walk away, head held high.
Problem number 3: You are still emotionally attached to this girl. My advice, throw yourself into anything and everything which makes you happy, as her seeing you happy without her will throw her off her game and she won't be able to pull the same old tricks on you again. Another thing you should do is to always be around one or more of your friends, so when you see her, you can look to your friend and start a conversation, which will make her feel as though you are over her which will do exactly the same thing as being happy will.
NOTE: I truly think that making her feel bad will not help, BUT if you can honestly say to yourself that it will, and you know her well enough to pull it off, then that is your decision and I hope it makes you feel better.