Adopted 10 month old skittish cat, loves our other cats but still terrified of humans. How and is it possible for us to help her feel safe?

Hello,

I adopted a cat who was around 6 months old last year, late October. She was described as skittish by the volunteers who were telling us about her. Now, we have two other cats one who has been with us for almost three years and the other one for two. the first one we ever adopted was able to warm up to the other cat within a few weeks. But, I've realized that with this new cat, we'll call her bella, isn't really warming up to us in the slightest. She is insanely friendly to our other cats who still swat her away and hiss at her when she comes near by. She would always be near them and has shown a lot of curiosity towards them, but runs away if me or anyone else comes near by. We somewhat co-exist, she would hide under a shelf, or near one of the cats if she was in the same room as us. but other than that, she would run away and avoid us if we come too near. The most she has ever done was sniffed my finger after i stretched my arm out towards her and then run away if my finger slightly touches her nose. my parents want to give her away, since she hasn't warmed up to us, but i don't want to do that. even though i havent built any meaningful connection, i still dont want her to go back to the shelter.

is there anyways to help her feel safe around us?