Twins?

'Danielle why do you have a bruise on your arm and a cut on your cheeck???' You asked
'It's nothing.' She said holding back tears
'I don't believe you, tell me Danielle i'm your sister.' You said

You and Danielle are twins, but you and Danielle are very different. You are very strong, athletic and model like while Danielle is smart and nerdy. You and Danielle are in different high schools for one reason. Since middle school you'd beat the kids whenever they tried to mess with Danielle until now, she decided to have different schools so you both could focus on yourselves. But one day you tried talking with her but she ignored you, this continued for months until you cornered her and you made her tell what was going on and so you switched you identity with Danielle to beat up her bullies. But what if you fall in love with a boy???