OK, long story short, and I'm leaving out A LOT of minor details.....
Me and this girl had been talking for about 1 1/2 months during January/February. I'm 19 and she's 21. We went out three times and hung out at her place a couple of times, as well. I liked her, and I got the impression she liked me too. We would call or text each other nearly every day, and I really started liking her. Over the past couple of months, I've gotten to know her well, and I really care about her.
Well, before this past week, for about two weeks, I would call her and ask her to go out or something, and she would say yes, then flake at the last minute. This happened three or four times. I got her something for Valentine's Day, and even called her the Sunday before and asked her out, and she said she would like to go out for V-Day. Well I tried calling her all day that Monday, and she never answered, and never called me back. I tried calling her the next day....no response. So I talked to a friend of her's that day and she told me that the girl I liked had a lot going on and that she's been with this guy she's been dating for a couple of weeks, and she said "Well, he's kind of her boyfriend now, I guess."

You can imagine how surprised I was. So, I gave her friend my gift and asked her if she would please give it to her. Two days later, I got a card from her in which she told me how she loved my gift, how much it means to her, and how thoughtful it was of me. She also said she was sorry she hasn't talked to me in a few days, but that she's had a lot going on and that she hopes to talk to me soon.
Which brings me to today. I haven't tried calling her since last Tuesday, but I tried today. No answer, and she still hasn't tried calling me back. It's obvious now that she doesn't like me like that, but she won't give me the chance to talk to her and tell her that I just want to be her friend.

I know you're all probably wondering why I'm even bothering with this girl, but I really do care about her, and I just want her to know that. If I could just talk to her and tell her these things, I would stop calling/pestering her and back off, but I haven't had the chance to tell her since last Sunday. Sooo, I know I'm going to see her friend on Friday, and I'm thinking about buying a blank card and writing something to this girl about how I feel, and giving it to her friend to give to her. As of now, I feel like this is my last resort, but there's no other way...she won't answer her phone. I'm pretty sure she's not answering because she thinks I'm going to ask her out again or something and she just wants me to get the hint, but seriously, I'm not even trying to go after her anymore.
I'm just asking for some of your opinions on what I should do in this situation. I feel like if I don't let her know these things, it will bug me from now on. But I feel like if I do this, even if I don't hear from her anymore, at least I'll feel better that she knows how I feel. If I give her this card, I know better than to say things like "I love you" and stuff like that, because I don't love her, not like that. BUT, I do care about her very much.
Basically, if I do this, all I'm going to say is that I care about her, I'm here if she ever needs anything, and that I'll leave it up to her to contact me. What do you think?