First of all, her home being in a bad area of town seems like a pretty big thing to me. I wouldn't want to be driving somewhere I don't feel comfortable, let alone getting out of the car. So there's really no way I would leave my child in that place, even if her actual home seems safe. You just never know.
I personally, am not a big fan of day care. I think that kids tend to get over looked and they just don't get enough one on one attention that they need. Especially if you're worried about her being prepared for school and those things, I don't think that day care is that way to go.
As far as the babysitter your fiance suggests, from what you've said does seem like a good person to care for your daughter, but I'm not so sure about teaching her the things she needs to know.
What I would suggest is maybe look into hiring someone, like a nanny, to spend one on one time with her. Honestly, this is the best attention your child could get. Don't be afraid to hire someone young either. Your daughter is old enough now that all of the new born scariness is gone so it's nothing a 19 or 20 year old couldn't handle. Plus, someone who is working for you personally can adapt to your schedule, come to your house so you wouldn't have to worry about taking her to somewhere unfamiliar, she would have all of the comforts of hoime, no baby bag to pack every day, no dropping off or picking up. And, a nanny would be willing to teach her anything that you felt it neccessary for her to learn before she's school age. You also have someone who is attached to your daughter and will love her so you can feel at ease while you're away. Most people think that hiring a nanny is too expensive or out of their price range, but most will accept a weekly rate and work with you.