"Stuck with" is a colloquialism. It's just saying that she'd planned to make X profit and instead will end up with a loss. There's plenty of ways to make a loss: sell it at a discount (near or below what you bought for) or spend so much effort making sales that your opportunity cost is more than your profit. The article's point isn't about how she's going to get rid of her useless inventory, so it just uses the shorthand that she's not selling at Amazon and has no immediate profitable back-up plan.
The fact that they were stuck with inventory in the garage just means they had no idea what they were doing.