As with any film or book series ...

Watch them in the order they were made/released!

And, since she's never seen them before - DO NOT SHOW HER REVISITED, OR THE 1997/2004 SPECIAL EDITIONS! Please show her the 1977, 1980, and 1983 theatrical cuts, like it's meant to be. Use the GOUT for IV, Adywan's restored ESB theatrical for V, and the GOUT again for VI.

Or you could wait for Harmy's ROTJ theatrical restoration to be done for VI. ANH, on the other hand, would have to wait until after Ady finishes ESB:R, as he's said he'll do an ANH theatrical restoration for that one once he's done with ESB.

Then, when you get to the prequels, show her Adywan's restored theatrical cut of TPM, then the DVDs of II and III.

And if you do show her Revisited, please make it the Purist version.