trouble with DD2

[amandaf64]

DD2 is 15 and she has not been herself at all recently, she has been a bit off the past year but I had put it down to teenage girl hormones as I went through the same thing with my oldest, however over the past few months she has been out of character, either being extremely withdrawn and introverted or being hyperactive and very impulsive, going out all day and not coming home until 11 or 12 at night on the weekend, and she has also changed to a restrictive diet (she's a vegan now) and keeps going to the gym and skipping meals.
I don't know what's wrong with her and I'm worried sick, I've tried to speak to her and DD1 has tried speaking to her but neither of us have gotten through to her, she just shuts off and either cries or gets very angry and begins to throw things and scream like a maniac.
I don't know how to talk to her as I've never gone through anything that severe, I'm also upset because I've always told my girls they can talk to me about anything, but she obviously does not feel comfortable talking about it with me.
I was just wondering if any of you can give me a hand, how to approach her etc because I really have no clue.

[CaptainSweatPants]

The gym & restrictive diet & moodiness trigger warning bells to me

Is she very thin? Does she eat a meal at home with you ?

[amandaf64]

She's just a little above average weight wise but she's definitely not fat.

And she eats the majority of the time with us and we're monitoring what she eats to ensure she gets proper vitamins etc on her vegan diet

[Chottie]

Do you think she is being bullied? or maybe she is depressed? she definitely doesn't sound happy.

Could you and DD1 go to the gym with her and make it a family outing? Doing stuff together might be a way of getting her to open up to you.
Has DD1 noticed anything usual on DD2 facebook or social media sites which might have triggered this behaviour?

Regarding the meals, I'm not sure whether you all eat the same meals, but maybe once a week you could all eat a vegan meal and DD2 could be involved in choosing the menu and preparing the food?

Forgive me if you already do this stuff, but I am just trying to think of ways to engage your DD2 with the family more.

[amandaf64]

I don't think she's being bullied, she's fairly popular but she's very upfront which has got her into trouble a few times.
And I know DD2 has got a blog tumblr thing but DD1 says that she doesn't post anything unusual just fashion, things from her favourite TV shows, bands etc.
And we do include her in our meals, like I'll make a stir fry and she'll add tofu and I'll put chicken in mine and things like that.
And I have offered to go with her to the gym before but she's refused saying that I'll embarrass her. She's so stubborn so there's no way I'm changing her mind.