Girl really likes my boyfriend and is trying to fight me for him?

[Dee]

Me and my boyfriend have been together for 7 months. He has this really good friend who I have never met who goes to a different school. They met in year 7, she's a year older. I've never had any problems with his friends, we've always hung out and I've talked to a few I've never met, but she's different. She really likes him and my boyfriend came and told me about it and how she'd been flirting with him at a party the other day and over Facebook. She had been looking up my profile and saying how I needed better pictures of my blue eyes (he likes blue eyes A LOT!!). My boyfriend says she wants to practically fight me for him, but I don't want to cause any trouble. I trust him, but it must be exciting to have an older girl after him, he seemed pretty proud. How do I explain that this, and his friend, are hurting my feelings? I'm worried he'll leave me for her, and I want him to tell me he won't do that to me. I know I shouldn't be worrying, but is she purposly trying to mess things up for us?
I frogot to mention this- when I asked how old she was, he said she was a year older and then told me not to be mean as she was a really good friend. He defended HER. He never said anything about stopping her flirting with him when they were talking last night, and she knows how long we've been going out for after looking on his profile. I don't know if he defended me when she made some really harsh comments about me.