Taming & Socializing 4 month old feral kitten

Quick background - I work as a Doctor's Assistant at an animal emergency hospital and often have good samaritans that bring in stray kittens and cats. A couple of months ago I adopted a 6 week old stray kitten that was found eating rat bait. I took him in and the first few hours of him being in my apartment with me he was hiding and incredibly scared. That night I set him up in the bathroom and left him alone. By the next day and his first real meal, he was following me around and meowing and wanting to be cuddled. It took him a few weeks to get used to the idea of being held. But he came around fairly quickly. He is now 4 months old and my crazy lovable kitten named Bellamy. 

I vaccinated Bellamy and thought that during my 12 hour shifts he would do well with a friend. I have pet sat for other cats before and he's loved everyone who's come through the door. I tried to adopt other strays that had nowhere to go but after a few of those falling through when they went to the shelter I decided to wait for the right to kitten to come along on her own time. I received an email a few days ago from a co-workers friend asking me if I wanted to adopt one of four kittens she found under her porch. They looked to be about Bellamy's age and needed homes. I thought well hey, Bell was so easy, it couldn't hurt to give another stray kitten a good home. We set up a meeting time and I went to this woman's house to see the kitten. She's about four months old and terrified out of her mind. The woman didn't quite warn me on her being absolutely feral. She quickly trapped the kitten and got her in the carrier I brought and wished me luck with her. It was so quick that I barely had time to think of a plan on how this kitten would do with me. I've never owned cats before, Bellamy being a great first kitten to have. Maybe a little too great because when I began to research how to socialize this new kitten and make her feel safe I saw a load of posts saying that she's too old to be tamed or that she will never actually be able to be touched. 

I set her up in the bathroom and left her alone for quite some time while I read up on what to do. The woman who gave her to me has been petting her but unable to hold her. From most of the advice I see on this site people are saying I should leave her alone for about a day so she can get used to her new surroundings. She hisses when I come too close but doesn't swat or lunge at all. I think she's too scared to make much movement. I checked on her just now and saw that she used the litter box and ate all of her wet food but migrated to the bathtub where she meows from behind the curtain whenever I walk into the room to change her litter. I set up a safe place for her in the bathtub since that's where she prefers to be and kitty proofed it. I can't help but feel guilty taking her in because I want what's best for her but she was pretty much just handed to me before I could even get her history. I work a lot as I am a 20 year old trying to save up to go back to school. I work 12 hour shifts 3 days of the week and I'm wondering if that would get in the way of socializing her. I don't even know where quite to begin. I am bringing her to my work on Monday to get tested and her first set of vaccines. I am afraid though that it will set her back a bit if I put her in a carrier and take her to work where strangers will be handling her. 

I just want to know what the first steps are into socializing her and if I am even a good fit for her. I hate the idea of having to give her up because I want to make an honest good attempt at possibly taming her. I also would need advice on introducing her to Bellamy, who is already so excited knowing she's in the bathroom. It would be great if I could get some tips on how to handle her or what she's going to need so that I know if I'm a good fit for her or if I'll end up making things worse for her. 

Here is a great video that tells about the taming of feral kittens.  It starts with the rescue of the kittens and moves on to their socialization.  You will find awesome tipsl  Be sure to watch all 3 parts

http://www.urbancatleague.org/TamingVideo

I dont think being gone all day 3 days out of the week is bad. Most of us have shorter workdays but its mon-fri. The kitten will also have company of Bellany pretty soon.