<human>: I've known my best female friend for about 2 years now. I'm a year older than her, and I go to college about 250 miles away. Because of this, I don't get to see her very often. We've been friends for about 2 years now, and we're extremely close. We talk everyday, throughout the day, and there's nothing alot I don't feel comfortable telling her.

She's graduating high school soon, and her 18th birthday coincides closely with her graduation date. I want to get her something really special. She's hugely into aerospace, and there a photo poster I'd like to get her signed by a celebrity in the field who Reddit knows very well.

However, this gift is extremely expensive (+$50 USD). I've told her some details on what it's going to be, as I'm terrible at keeping secrets from her. But I haven't told her how much it will be beside that it is a lot, but that I'm comfortable with it. She however is not. She thinks it's a waste of money, and that she doesn't feel comfortable accepting something this special from me.

I still really want to get her this gift however. I know she'd love it, and she means a lot to me. I think she feels bad accepting something like this from me, because she tends to me the meaner one in our relationship while I tend to be the softer one. I know she doesn't ever mean it, but I think she still feels bad. You only turn 18 once, and you only graduate high school once, and although I know it's not a big deal, it's still a big life milestone. 

I want to get her this gift, but I don't want her to feel bad. How do I convince her that I'm doing this because I care about her and I want to get her something special? Or am I wrong in still wanting to get her something this expensive, and that I should just respect what she wants and get her something cheaper?

Can you give me a shortened version of the text?
<bot>: Best friend of 2 years is graduating soon/18th birthday, want to get her a special, expensive gift, but she is apprehensive accepting something like that.