It is entirely possible that your dd2 is just trying to assert herself as different from your dd1. A completely normal sibling reaction.
My dd1 couldn't care less about clothes, pink or not - she has severe ASD and the whole gender thing just does not occur to her (thankfully!). And so (for eg) she has whatever clothes, in a whole range of colours, it please me to buy.
Dd2, however, will not wear some of the hand me downs. She does care about clothes (also ASD, but much higher functioning) and will only wear the ones that she likes.
Dd2, btw, used to have short hair - a crop. Because she refused to have it brushed, and hated having it washed, and tying it back was a struggle when she was about 2. So the easiest option was a crop.
She now has long hair (by her choice) and most of the time or of school has it loose, as she still dislikes having it tied back.
I agree with everyone asking why you have been asking if your dd2 is a girl or a boy. An odd question.
My ds (only 3) was in tears the other day as we went to his sisters school and he realised that when he goes there he won't be able to go into the 'pink' changing room for sports (grr at the school having different colours for the changing rooms, but to be fair, school colours are navy and raspberry). His favourite colour is pink, currently.
I explained to him he could still wear pink as part of his sports kit, but he is a boy and needed to go in the boys changing room.
Dd2 (and this made me 
- clearly some of my words have sunk in over the years) said 'ds, don't worry. Some people think colours are for girls and boys, but that's silly. You can still like pink. You do have to go into the boys changing room, but you don't have to change your favourite colour'
The only wanting one thing to wear (eg pirates) is completely normal. When ds2 was 3, she would only wear red. Everything had to be red - toothbrush, clothes, plates, cutlery etc. That was a nightmare as wverywhere we went, she got given pink as she is a delicate girly looking girl (even with her short crop!). She would also only wear trousers until she got to about 3, then it was only dresses for years. Now she's back to wearing a mix of leggings and dresses/skirts, but won't wear trousers at all. It's all just personality and her trying to figure out what she's comfortable wearing.
Ds wears trousers or leggings, but jumps at the chance to dress up in his sisters old dresses and be a princess. If he makes a crown, he is 'princess ds' not prince or King. I don't think he is transgender, he just thinks that it's princesses who like glitter and sparkle, so he pretends to be a princess. He knows he is neither a girl nor a princess. But he wants a pink sparkly crown so he pretends to be one. A bit like when he dresses up as the gruffalo, and needs purple prickles, or dresses up as a lion and needs a mane and tail. He is adamant he wants long hair, btw, because he cannot bear having his hair cut. His solution (and one that works for now since he is t in school) is to have longer hair. Fine. School will also be ok, as long as it is tied back (the head thinks she is being clever in threatening hair ties to boys to get them to have neater hair, that won't work with ds!). I expect sometime during reception he will end up conforming to what the other boys do, but we'll see. If he wants to keep longer hair, then so be it. He will have to stick to uniform rules (off the face/tied back for sport), but that's hardly a big issue. It won't make him a girl, although I expect he will get comments from other children, and even other adults (which is why I expect he will end up conforming, for an easier life. But his fear of haircuts is very strong, so it could take a while).