Yes on the rose overtone Freshadamas, or their equivalent, and I agree that an 18" strand is the most versatile. Shorter is more formal and slightly longer can reduce the number of tops that will look good with it.

If you still want a longer necklace, I would go a little longer than 22" and get a nice pair of pearl stud earrings to complete the look. Just call the vendor to add inches if there isn't a selection.

She's going to look terrific!

Cheers,
Blaire