My friend just told me today that for a whole year and a half she "hated my guts"?

Today i remember my friend asking me if i liked the poster she got me, i said i did and then we started talking she was joking around said ya it will look so great in your room and i laughed because my room was really formal and it is an MCR poster. we were making drawings and filling them with words that represended our selves. and she asked me what i was drawing i said a heart with thorns she asked why and i said it stands for a gaurded heart and that was it. she asked me what happened to us we used to be best friends? it was true but then she told me that last she secretly hated my guts and that she only recently started liking me because i had change for the better. I really dont know what to think of this i just found out that one of my best friends had hated me but at least she told me, i guess, right? she said she likes me now should i forgive her fro using me?