Teach in levels.
My girlfriend is apolitical but agrees with things from many political ideologies.
Ever since we have been talking more about the history of Spirituality and how jews have negatively affected it, she has opened up to NS. She now says it makes sense.
I'd say you can rest assured that she's not completely programmed against it, and if the conversation ever arises, you two can talk about it.
Just make sure to always give the facts, don't make anything up if you truly don't have an answer.
This is a highly slandered time and NS is a highly slandered ideology. So we can never have the "perfect evidence" everyone wants unless there is also spiritual advancement involved.
Mostly, you're fine to talk now, just be careful as per usual.