Wow. Things just don't seem to swell. Maybe you two had your good times,maybe your friend is just going through a rough time in their life, or maybe this person is just straight up not a good friend. Either way, your friend doesn't seem good for you. List the qualities of a good friend, and how you yourself like to be treated. If they don't match up with this person, well, either try to fix your friendship, or just try and move on
You are on a good way. Flirt could mean you guys only met or fell in love a few days or weeks ago, but that doesn't mean you can't fall in love! Flirting is something people do a lot, you see some one you like and in that case you of course you hope that person to like you too! When you get to know this person better you could be an amazing couple! My advice: Hang around them more, try and talk to them and once you achieved that: Do something fun together! If you don't want to go on a date, just ask some friends with you. Could be a lot of fun!