<human>: Hi Reddit,

Here is my situation. I've been with my girlfriend for almost three years and I'm pretty happy with our relationship. However she can be pretty stubborn (I'm not complaining, I can be the same) and sometimes I really do feel I'm right and instead of listening to my arguments, she just get mad and reverse the situation. Days after, when she realize she made a mistake, she does not even realize I've warned her. 

Here are a couple of examples: she took useless and expensive online classes (to learn English, but her English is already perfect, she got bored and now it's wasted money), she went to a company she did not like and left three months later and more recently we got an argument about a silly thing: she wanted to book a flight for a trip together (cheap ticket) in April but I've told her I won't have vacations and I wanted to visit another country. She got mad, told me I'm not fun and even if she hides it, I know she resents me... 

Don't get me wrong in our couple she's most of the time the mature person but sometimes she got extremely unreasonable. I've tried to talk to her about this, but she's very proud and does not want to hear about it. The worst part is she's an extremely talented negotiator and is very strong willed (part of why I love her :p). So it's very hard for me to win an argument. Most of the time she ends up turning the tide in her favor and I don't even know how she did that.

Can you condense the text into three sentences or less?
<bot>: My girlfriend is much better than me at arguing but I really don't know how to reason her from time to time. How can I handle this?