I'm Defunct After 15 Months!

The title says it all - after a mere 15 months of being the top dog in Isabelle's life...I am now surplus to her requirements.
For a while, she has been very fond of my mom and dad - my dad in particular.  I assumed that it would plateau, and she would lose interest, but the opposite is happening. Every time she sees them, she seems to fall more in love with them, to the point where she melts down if they leave the room, or when she has to go home. And I am talking sobbing, tears, screaming, throwing herself at them/chasing them, the works.
All this, by the way, when I am standing right there. Because obviously, I am no longer important.
Even at home, away from my parents, I am no longer top dog. That title now belongs to daddy. All I hear, allll day long, any time there is a little noise is 'Daddy?' with a hopeful face. When he is here, I am  not needed. She falls...it's him. She wants to play...it's him. Meanwhile, muggins over here is called upon at milking times, and that's it. If I try to take her...she cries. When we are home alone, or out somewhere together with other people, she adores me. Clearly that's only because she has no other choice, because as soon as one of the others steps through the door, I'm out, they are in.
I spoke with some friends about it, and I was relieved to hear I am not the only mommy who is no longer required. Although it sounds quite funny, and it is of course very sweet that Isabelle loves her grandad, granny and daddy so much...........
It hurts.
It really hurts. To see her fall over, and try to comfort her, only to have it made clear she doesn't want my comfort. Or to have her cry when I lift her from someone else's arms. That hurts. It should be the other way around, surely? I should be the one giving the smug looks to other people when she doesn't want to go to them. I should be the one saying 'It's just a phase, she'll get over it', not hearing it instead.
Simon tells me it's because Iz takes me for granted - unlike the others I am always there with her, and that when I start work again it will be different. But that's not very much consolation now.
After 15 months of being a mummy's girl through and through, she's had enough of me. Her separation anxiety has reached it's peak. It's a pity it just has nothing to do with little old mommy over here....