I think it is wonderful

There is nothing "wrong" with your label. It makes your quilt even more special. If you like it, go with it. Because of the size, I would stitch it across the diagonal side just to hold it in place. Carefully stitch by hand so none of your stitches show through on the front. Even after many washes, it will be there to remind the recipient just how special she is.

In my humble opinion it's too big. The largest one I've ever done is about 5 1/2" x 8 1/2"...being too large takes away from the actual quilt.

It may be a little big but I would hand stitch (like binding) the long edge of this label to the quilt. You don't want dust bunnies to get into the opening!

When I do a label that is incorporated into the binding/edge, I use binding along the free edge, fold it over just like all binding, and sew that down to the quilt as well.
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I usually make my labels 5" to 8", so by that standard this one is big. All that matters is that you like it. It will be very legible. I agree with those who say to sew or tack it down in a couple of places in the middle so that it won't be baggy

If you're worried about the label bagging after many washings you might think about using a double-sided interfacing to tack it down. I also use a triangle shaped label but not quilt that large. I have a template in my Embird program that I add all my lettering into, then stitch a one-sided iron-on interfacing to tack down the edge that will be handstitched as the other 2 sides will be stitched along with the binding.

I agree with Kathy that you should stitch it down in several places in the middle just to be on the "safe side", and you don't have to go all the way through the quilt, although it could be additionally attached by quilting over it.

The label is a design element, and the pink is a bright spot! I don't think I'd change it.

Some stitching in the center of the label would be good. How about putting invisible thread in the bobbin and making a few scribbles in different places on the label. OR, put the invisible thread in the top and go over a few places from the top of the quilt. That would hold your label in place.