Too nice?

First of all, hi all! This is the first time i have made a blog. I hope you guys will not find my posts boring and will give comments that could maybe help me.

Here it goes:

A few days ago, my friend and i were buying time before tutoring after school. We talked about our schools, people in it, our friends...basically anything. (My friend is from a different high school to me).

We somehow reached the topic of niceness. And she told me that i was too nice for my own good, and that i would be 'stomped on', as she so kindly put it. She explained that i always saw the good in everyone and helped them without even questioning their motives. To prove her point, she asked me to check her maths h/w. I, of course, agreed, thinking she really did want me to check her maths work. But after checking the WHOLE thing, she told me that she didn't really need me to check it, but was just trying to prove her point.

She told me that i needed to be bitchier. But i don't agree with her. If i became bitchy, wouldn't i just become a horrible person? Even when we were bitching that day, i felt sort of bad. I would totally regret my actions if the person found out. I wouldn't want to lose a friend because i talked about her behind her back. So why would she want me to be bitchy?

Actually, i can be a bitch. I am a bitch, but i don't like to express those bitchy thoughts out loud as i don't want to rub off the wrong way. It's like i have two personalities: the friendly, nice, smiling and talkative side of me, you will find at school or hanging with friends but at home, you will find the short-tempered, jealous and absolutely horrible side of me. I hate the bad side of me, it makes me feel dirty, ugly and horrible.

So what i want to know is: am i really nice? Should i be bitchier, like my friend told me to? And if i should, how much bitchier should i be?