what i've learned in my life time is "what goes around comes around". the things i've done when i was young and nyeve did come back on me when i was an adult. life is an experience, and you learn through wrong choices, hurt, and everything else in between.
you are a growing adolescent, you are still in the phase of puberty.
i am 33 years old and my son is 13 years old. you almost my son's age, and the women your with is almost my age.
what this women has done is wrong, what you failed to realize is the kind of person she is, and what she is capable of doing.
for example lets assume yall run away together, what happens when she gets bored with you. from what she did i wouldnt be surprised if she would sleep with your friend.
i talk to my son about his character-moral, ethical, quality. and this was done out of bad character from you both.
this will be a double hurt whammy for your brother, and probably dont deserve for his girlfriend or his brother to hurt him like that.
your living in a fantasy land if you really think this thing will last a long time.