You need to report this to their command. This is a huge breach. If it's not corrected, they'll both be written up and possibly you guys could lose the allowance, lose rank, etc. The military will absolutely call that stealing! This is coming from a former military wife.
I had 150 rsvp for my wedding, but I had told them that it was a dry wedding (our choice, I wanted to be clear headed so I wouldn't miss a minute) from the start. Very, very few of my friends came even though they said they'd be there. Reduced the actual attendance to 75 people and we wasted a ton of money. I decided I no longer wanted them in my life. No regrets. NTJ