Dealing with Twin Girls?

Help her with her lines. Go to all her performances. Take an improv class with her. Be the chaperone for band trips.

I also think at 15 she's old enough to just point blank ask her what she needs from you. Some girls at 15 aren't so much into mommy.

Do you share interests with Maddie or with Meghan?

Were you the cheerleader and outspoken girl? Or were you the artsy keep-to-yourself type? Likely, my guess would be that you and Maddie are more alike and so you are drawn to eachother more. So if that's the case, and even if it's not, try to get more interested in Megan's likes/dislikes. Go to art shows, take her to a special musical event - just the two of you. Have a heart to heart and just let her know that you love her and are there whenever she needs to talk to someone. Some kids are just kinda quiet (I was one of them) and have a hard time approaching someone (even my mom) with a concern or problem. Mom had to work hard to get me to 'spill the beans' on whatever was going on with me and school and what-not.

Communication.
Communicate with her and express TO her your feelings and love for her.
Every kid has different personalities, but they still all need a Mommy's love.

If you don't want Meghan to feel less important... then just TELL her. Tell her "I love you and you are your own person. I'm proud of you. I don't want you to feel less important, because you are so unique and I really admire that in you. So what can I do that would help?"

OR, consider that your Meghan does not even feel like an odd-ball or less important. I mean, did she actually tell you, that she feels less important? Maybe that is just your own.... apprehensions about her. That maybe 'you' feel she feels she is less important? Maybe she doesn't even feel that way.

And, just carve out some time with her. Doing what SHE likes. Show an INTEREST in her and her own proclivities and talents and thoughts/feelings. A kid, really needs that. They need to feel "accepted" for WHO THEY ARE.
That is key

Or just ask her "What do you want me to do, to help you? Even if that is just hanging out."

Communication.
With each child, it will be different.

Maybe you worry about Meghan, but she is just fine.
Ask her.

And per Maddie, maybe it is not that she needs more "attention" but that... she is just more communicative and able to express herself more.
Just because someone is expressive, it does not mean they are an attention getter.
Sometimes, the more silent person, needs more.

Know your child and accept them for who they are.
Then, show an interest, in the child for who they are.
That is a way to bond with that child.
That is what my late Dad did with his kids. And we all knew we were different from each other, but that he bonded with each of us differently... per OUR personality. He really just knew us and accepted us for who we were. That is golden.

I have a girl like that too, I've just learned that some kids are just quite and she will come to you when their is a actual issue that needs to be adressed.

Maddie has always wanted more attention you said. Maybe Meghan needs more. I would tell her you love when you can and just try to let her know in little ways that you care about her as much. You can't have the same connection with each child, as you know, so just be sure she knows you love her in any way you can and ask about her day and issues just to draw her out. Sometimes the more outgoing one takes all the attention when you need to try harder with the other one. Hard to do when more than one to to love. And so many personalities, etc. I wouldn't 'worry' about her but just try hard to let her know you are there for her too. Maybe take them out separately to shop with you or something to help her be able to open up more to you. Maybe they wouldn't enjoy shopping with you but just little things to let her know you're there for her.

You could share a journal where you write back and forth... sometimes more introverted people are more comfortable sharing feelings in written form than in spoken conversations... ditto w/texting, email, chat if you use any of those things w/them. You could take an art class together or yoga, etc. to find some special bonding time for just the two of you, if possible.

If she likes to read, pick up the books she is reading and read them alongside her so you can talk about them- your own little "book club" and then maybe rent the movie together afterward, if there is one.

You mentioned drama club.. maybe there is a play that the two of you could try out for together- over the summer, possibly, if it's too busy during the school year. Or maybe the two of you could work on a play for your family to perform... it could even be super-silly, like where each of you acts like another family member in various situations (keeping it lighthearted of course, so as not to hurt anyone's feelings!!)

If she is closer to her dad, I would definitely encourage that and make sure they have bonding time together and he is realizing that he is really her "rock" right now through these years.

Sounds like you are on the right track already just by being interested in her and wanting to spend time with her- kids pick up on that and just "know" when their parents care.