How can I [21F] be closer to my newly adopted sister [7F], who is seemingly afraid of me?

She was adopted 4 months ago. I don't exactly remember the whole thing and I didn't meet her before she was adopted, but I think she's been an orphan since birth. I think her mom died at birth :(
So I was really excited to meet her and she didn't respond positively to my presence. I met her on the night of the day they adopted her and she was in her room, which was my room and still has some of my stuff. I started real slow and tried to keep it low key, just saying hi and asking her her name, etc. I knew most things about her but just wanted her to open up a bit.
Didn't work. OK, she's shy, she needs time, this is all crazy intense for her (I can't imagine). OK. But it hasn't worked so far either. I tried to talk to her about the books, video games, toys that are still there that I used to play with and that didn't seem to do much either. I mean she would grab the toy and sort of explore it on her own but not really reply to me or really acknowledge me that much.
Also, mom or dad have to be present in some capacity otherwise she gets scared of me. They don't have to be right there, but they introduce her to me every time I'm there so she knows they are there around. One day I was helping around the house and went up to her room and tried to say hi but she got scared and hid in a toy castle/house thing.
For her Bday last month I got her special order plush doll that is, well, her. She has a red-transparent birth mark on her left eye and I got her a doll with her skin tone and a that very same birth mark. She LOVES it but doesn't acknowledge me either. Parents said "She got it for you", etc., but that didn't open her up to me either.
I wasn't trying to buy her love or whatever, but I figured maybe she would associate the doll with me and maybe open up a bit. That didn't happen and I'm not mad or anything, but I kinda want to be closer to her and she's a bit distant.
What can I do? I figured that maybe some regular exposure would help us and she would become used to me but it hasn't happened yet? What can I do that is low intensity but sort of help us be closer?
tl;dr: Adopted sister doesn't like me that much. How to be closer to her in a low key way that doesn't push her or makes her feel forced?


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