All 24 fighters on the card weighed in the night before the fights, and Moyle (114) apparently missed her 110-pound requirement by four pounds.
Alba, 30, took to social media to express her displeasure with the situation.
"Opponents not making weight is so disrespectful. Especially if u do it time and time again abusing the system," Alba tweeted.
One of Moyle's past opponents, Delaney Owen, claims the Florida fighter did the same thing for their Fighters Source bout in 2012.
"@jessphilippus @WMMANews she didnt even try to cut the weight. They gave her time and she refused to try she said she wasnt gonna do it," Alba tweeted later in the day.
Moyle's team knew Alba traveled a long way and spent a great deal of time to get to the event in Las Vegas, so they knew she wasn't about to back out of the fight just because their fighter was four pounds over the limit.
Alba and Moyle agreed to fight at 110 pounds, without a one-pound weight allowance.
Moyle weighed in at 114 pounds, while Alba was on the mark at 110 pounds.
Moyle was allowed an extra hour to cut and she declined to attempt it.
"How is that fair to me? I busted my a** the last four pounds to make the weight I agreed at," Alba said. "She is fresh and hydrated and comes in with her hair and makeup all done."
Alba says the fight will go on just because she traveled a long way and doesn't want to disappoint her supporters.
“Tuff-N-Uff: The Future Stars of Mixed Martial Arts” is set for Jan. 24 at Las Vegas' Orleans Hotel and Casino.
Analysis: In the pros, the fighter who doesn't make weight often has to give a hefty portion of their purse to the fighter who is on point.
In the amateur ranks, there's no money involved, so there's almost no incentive to make weight. An interesting idea is to dock the overweight fighter one point, so they are at a disadvantage on the judge's scorecards in case the fight goes to a decision.