calling all moms of multiple daughters

Maureen • Wife & Mama of 3. Horror&Halloween. Harry Potter obsessed. Photography. Makeup. Certified Chef. Vintage everything.
So I'm currently 21 weeks with my second daughter. I'm extremely excited and so is my first daughter because she gets to be a "big sister". She's 3, and will almost be 4 when the new baby arrives. But here is my fear:
I absolutely ADORE my daughter. She is everything I ever wanted in a child. She is my entire world. My husband and I pride ourselves on how perfect she turned out and how smart she is. We completely devote ourselves to her and make sure she is happy at all times. My immediate family does the same thing. She's the only child. So now there's a new one coming and I'm scared of her losing any attention or feeling left out. I was hesitant to even HAVE more children because of this reason. I'm also super worried that I will always favor my first daughter and not know how to divide my love or feelings. I feel bad for even THINKING like that.. it's just one of those things I worry about. Like I guess when my second one is born my heart will grow or change. I'm just nervous about what if something in the back of my head will always love my first daughter a tiny bit more? 
Has any other mothers experienced this? I wanted a boy so bad because I was nervous about this exact situation. But now I know it's another girl, and even though I'm thrilled, I just wonder how it works? Would appreciate any advice! :)