What regulation states that SMs are not authorized to receive an award for an inter-post transfers (since it is not technically a PCS)?

You don't get awards for PCSing. You get an award at PCS time to recognize your cumulative contributions to the mission and the team. It is not an absolute requirement.This goes for transfers as well.
An "impact award" is one where you earned it for achievement or excellence during the tour (overseas or CONUS) in a way that should be recognized as an act of it's own instead of a culmination of service during the tour. These types of awards are usually tied to one or two specific events where performance from you or your team was outstanding.

that's the problem with awards, everybody thinks their entitled to one. its up to your chain of command if you get one or not. so stop the winning and get over it. if your wife is a pfc like you then she hasn't been long enough for a pcs award, and as posted by another nco, being attached to another unit for a deployment is not a pcs move

AR 600-8-22 Section 3-1 D

There is no regulation that states you ARE authorized an award for PCS.
Awards are based upon the achievement or achievements cumulative during the tour. There is no guarantee that she will get an award when she changes duty stations, although I would bet that the unit has a PCS Check sheet that lists "PCS Award" on it and sadly those awards are what people get the most, and they are based upon pay grade and not performance. When I left Korea, the Command Sergeant Major, who was not a signatory on the awards form, wrote on the cover sheet, "Staff Sergeants do NOT get MSM's, downgrade to ARCOM" It had been written by a LT Colonel and a CSM's policy took precedence. The US army's Awards Program is BROKEN. How many have Bronze Stars for "Service" based upon the pay grade and not the job performance.

You don't need a PCS award if your unit does not want to give you one then you don't get one. This is even if it is a real PCS.

If you did something worthy of an award you would get it no matter what time it is. Awards are not dependent on PCS even though they frequently get awarded at that time.

As others have stated, there is no guarantee that you will receive an award. It all depends on what you did in the unit in the time you were there. The Company I served in for the last 2 years is a good example of every possibility with awards. We shut down back in October, and out of 50-some Soldiers, a handful were due to PCS/ETS within a matter of months. Of those few, some had awards written for them from the Company, some (like myself) had letters of continuity written and attached to a half written award recommendation, and some received nothing. Of the 40 or so that were intra-post transfers to other units, very few received continuity letters, and the majority received nothing. The fact is, the majority had basically just "done their job" and filled a slot for the time they were around. Again, it all comes down to the time you had and how you spent it.

Wife is filling a deployment slot for a unit on the same post but not within the same brigade.