"If I'm a woman and I lift weights, won't that make me look like a man?"
I hear this all the time! Women scared to train upper body for fear of developing terrifying traps and bulging biceps.
Well, I've got good (or bad, depending on your goals) news for you:
IF YOU ARE A WOMAN AND YOU LIFT WEIGHTS YOU WILL NOT LOOK LIKE A MAN - it's just not possible.
The main hormone responsible for muscle growth is testosterone.
Men produce anything between 2.5mg - 11mg per day; whereas a woman produces a mere 0.25mg!
So you see it really isn't achievable.
The women that you see with big muscles have worked hard, for years - eating lots and training very heavy. (Sometimes with the help of performance enhancing drugs, but not necessarily).
They look like that because it's how they want to look and have worked long and hard to achieve it.
Do not be afraid to lift weights and certainly don't be afraid to train upper body, or to lift heavy.
Even the smallest of bodybuilders in the bikini categories train upper body and they achieve a very subtle, feminine look doing so.
As you grow a little bit extra muscle you will start to develop aesthetic curves and burn more calories than before (aka burn fat).
You will increase muscle size over time but only if you are consistent in your training and your diet is spot-on for muscle growth.