How to Lengthen ElleMyra
Choose the size that accommodates your bust measurement, and you want extra length, here is what I would try:

1) Go up one needle size. This will make the whole thing looser, thus 'droop' more.
2) After sewing the rectangle tog for the armholes, remove the provisional CO and place all sts on waste yarn (You do this because the CO edge of the waste yarn on the provisional cast on will tighten the edge unnaturally)

Try it on. To add more length to the nape to waist, determine which edge will be the back and add a few short rows in stockinette to the back edge only to achieve a curved lower back (The back will still be several inches above your natural waistline) If you don't know how to do this, there are many online tutorials. What you want to achieve is a curved lower edge that is maybe 2 inches longer in the center back than at the seams.

3) Before BO the ruffle, place the whole thing on waste yarn, steam lightly, and try it on. If you still want more length, add another rep of the Reversible Eyelet Rib Pattern.