Should I give up on her?

My relationship with this girl is complicated. I am in love with her and see myself growing old with her. The thing is, I don't think we are even technically boyfriend/girlfriend. For 2.5 years, we have been doing things together that would make outsiders view us a couple. Every time I express my feelings to her, she always tells me that she is not ready to be in a relationship with another guy or that she is uncertain yet. I ask her to be forward with me and tell me if that is just a nice way of telling me that it will never happen between us. She says no, and truly means it when she says she doesn't know. Anyways, I put up with this 2.5 years, reminding her now and then about my feelings for her but the same thing keeps happening where she rejects me and tells me that she is not ready but might be ready in the future, possibly after graduation. She still spends time with me almost everyday, around maybe 3 or more hours a day, doing things a dating couple would do. We go out on dates quite frequently, maybe 3 to 4 times a week or more. If we don't go out, she spends time at my place. We are pretty much together every single day. I buy her gifts such as iPhone, designer bags, and designer watches; I buy them for her because she talks about wanting them a lot when we spend time together. She accepts my gifts and in my mind, a girl only accepts those gifts if she is truly interested in the man. A decent girl wouldn't accept expensive gifts like that from a man that she has no interest in right? She is not put off at all by my emotions at all and continues to do what I feel like is her toying with my heart. I really wish she would just be forward with me instead of keeping me around.

Anyways, fast forward to a month ago. She becomes friends with another guy and spends a lot time with him and his circle of friends, who are all males. I don't think it's wrong that I was naturally concerned about this. I confronted her about this and she told me that there is nothing going on between them. I also confronted the guy about it and he said the same thing. I did learn that the guy is always treating her to a night out, he always pays for everything. I have always done the same too. It really started to bother me that every time I wanted to stay in, she would jump ship and eat out with the other guys. It felt like I was being used and when she couldn't use me for the day, she would move onto the next guy to use. Out of anger, I asked her if she was using me and it led to a big fight between us. It got to the point where I was fed up and didn't have the desire to repair our "relationship" at all and asked her to never speak to me again. She refused to do so and pestered me about talking it out instead of ending what we had. We did talk it out again the same day and I apologized for being so possessive and jealous when she spends time with her new friend; it really moved me that she cared so much about talking it out instead of losing me so I continued to be persistent with our complicated relationship.

I can't help but still be jealous when she spends time with the other guy and his group of friends without me. Maybe it's because we have been doing things together almost every single day for the past 2.5 years and I agree that I need to stop being so possessive or clingy when it comes to something like this. It also bothers me that she never invites me to go out with them. The more she does this, the sadder I get. I try my hardest to keep it to myself but she is still able to notice. She says I'm rude to her whenever she decides to spend time with the other guy and because of this she has been ignoring me for the past week. I get really depressed when she ignores me. I text her to apologize and I try to set up a time to talk about it but she doesn't seem to care and doesn't respond. Not being able to stand this depressive slump I have been in, I ask her to be forward with me again and tell me if there really was even a chance between us for love. She finally replies and says that she doesn't need permission from me to spend time with other people and continues to ignore me. All I want is for her to tell me that it's over instead of ignoring me but she won't and still ignores me.

What in the world is going on in her head right now? What are her motives? I've read quite a few articles online dealing with this and says that girls are pretty forward from the start about whether or not they want a relationship. Why can't she be forward with me? Why does she keep me around like this? She is my first love so I'm inexperienced in situations like this. Should I have given up from the start? Should I give up now? I can't handle having to be so depressed about this anymore but I don't want 2.5 years of our complicated relationship to mean nothing now. I don't know what to do because it's so hard for her to just be open and forward about everything. I need advice from the female posters here to tell me what I should do when a girl acts like this.

Thanks