There seems to be a bit of confusion of late.
Scarlett, as this story points out, likes boys - namely "advertising executive Nate Naylor". She has had a number of high profile unions, like with Sean Penn and Benecio Del Toro. She was also married to Ryan Reynolds for a while. She had her phone hacked and we saw her bits.
Amber Heard, as this story highlights, prefers girls. She's also been in considerably less films than Scarlett Johansson.
They've shared a hairstyle a few times. That is all.