I would get a featherweight if the vintage factor is appealing. If she is new to sewing, every good brand (Pfaff, Janome, Bernina) will have an entry level that should not break the bank. No sense in going fancy features without even knowing your preference. I think that would take time for her to know and if she gets hooked this will not be her last machine.
I think a featherweight is a very romantic, thoughtful gift. Go with your gut! Plus a FW has the cute factor - it would fit nicely under a tree with a big red bow.