What does it mean if she is unreliable?

She is not planning on being serious with you. Unless she has a super-demanding life like two jobs and three kids, she would make time and effort to see you. If I like a guy, I make myself available. Another theory is that she is not totally single, balancing her time between two or more guys.

She Is not Into you. or hanging out with you. Period. I'm sure your a nice guy. however to her you do not mean much. And her flaking. DISRESPECT. my advice to you. Ignore her. She won't give you the time of day, then do not give her the time of day, Plus high school...well is high school and people change. In some cases people fall apart. Move on. In reality that is the best option. Reality sucks. BIG TIME. upside, I'm sure there is someone who would love your time and devotion. until that. FORGET about it. hope this helps and stay strong buddy.

It usually means that she is not interested in hanging out with you. If she has you as her lowest possible priority, "bailable" company, then you are clearly not considered worth her time and attention. Leave her to stew in her own S*** and move on to the sort of people who deserve you company and attention.

maybe she doesn't want it to be a frequent thing... she wants to keep a distance so its clear you two are just friends... there could be many reasons for this, either she's not interested or doesn't have time for anything serious. I think she just enjoys talking over the phone... maybe she's just shy... Try not to push her to hang out wait til she asks you.

When do you try to make plans with her? Is it the day of or is it before then?

When I get up in the morning my day is planned out. I have a lot of work, school work and other junk so I have to do that.

90% of the time if you ask me to do something later that day, I will say no because I already have a plan for then even if you asked me a few days earlier and I said I was free.

When she told you she would be free that night, she may have wanted to make a plan right then, but then when you asked her the day arrived she didn't want to go out then when you asked because she already had a plan for that day.

Plan things with girls in advance if you want to hang out with them.

When guys/people ask me todo something with only a little bit of notice it sometimes seems like they are just desperate to hang out with someone and everyone before they asked me said no...

I'm super busy though... it might be just me.

Confession: I'm a lot like this girl (from what you've wrote so far). I don't usually have my phone around all the time, and I usually get to texts that are a couple hours old, if not more. I say to friends that we should hang out, but I'm not proactive about it. Actually, I'm pretty introverted and reclusive, so instinctively, hanging out with people I'm not currently close to seems like a pain AT FIRST, but usually when I'm with them I have a lot more fun than I thought I would because of my mindset.
We may or may not be the same, but I just wanted to get out there that how she's reacting to you just might be a part of how she is, and not something that's you specific at all.

So that said, definitely be more proactive. A lot of people I see don't really take charge with plans, because they don't really have anything specific they want to do, so they don't care what they do, and there will be endless conversations about what to do because neither party is offering up specific options. If she's a busy person and you don't know her schedule. What I would do would be to text her that you'd really like to hang out with her sometime in the upcoming week/couple of weeks, and ask her if there's any particular day/time in her schedule that would be convenient for her, maybe if there was anything that she wanted to do. If she gives you something that sounds interesting, go with that, if she gives you a day/time that's okay with your schedule, offer something, if you think she might have car troubles, offer to be her ride. Be as efficient with your texts as possible, and try to take care of anything that might get in the way (like offering a ride) so there's no way that she can really turn you down unless she doesn't want to go. And be open if she doesn't want to hang out with you. If this continues even with you making up for her, then you might want to directly ask her if she doesn't like hanging out with you, that's fine too. (I don't think this is really the problem, though.) Best of luck!

I'm going through a similar thing with a friend of mine and it can be really hard to tell. I can't tell if he just says we should hang out to be nice or if he actually means it. At least for me I'm not stressing about it too much so I wouldn't worry if I were you. If you really want to hang out with her, try asking her in a more concrete way- like "do you want to do "so and so" at "x day" and "y time" if that makes sense. maybe she's forgetful or something and if you ask her in a way that makes the plans concrete you might get a better response

She might be toying with you bud. Friend or not, women get bored and just start playing games with. And when women get bored, they stop caring about you and you become their guiena pig. Don't let yourself become that. Women who flake on you repeatedly can't be trusted.

I'm going to try and make this clear for you. SHE IS NOT INTERESTED, RUN AWAY (not walk) AND DON'T LOOK BACK. I learned this the hard way, trust me on this.