If a NG officer and enlisted are dating, and the enlisted SM goes on AD orders, would that be in violation of Army policy under AR 600-35?

Along with rank, the other issue is chain of command...

Are they in same unit? Was the 1LT in a supervisory position above the SPC? Will the SPC be assigned to same or different unit while mobilized?

As I understand, the Guard has an "exception" to the policy to cover Guard Members who have a relationship outside of their Guard duty time, especially if the relationship pre-existed their joining the Guard. When the couple is under the UCMJ, that is when at drill or called to duty, the Army policy prohibiting fraternization applies. When off duty, the policy does not apply. Your friend needs to read the Guard exception and any state or unit directives to make sure they know the rules.

LTC Eugene Chu has a good point about Chain of Command.

Overall, the relationship is a bad idea. Even if the couple strictly follows the Gurad rules and there's no chain of command issues, the appearance of fraternization will still exist. Additionally, it will stress the relationship. IMO, both should consider moving on.

I believe Reserve component members, such as AGR or military technicians, who are on active duty (other than annual training) are subject to the policy.