Is this a pregnancy or the flu?

My girl has been on the depo shot (progesterone shot) for 6 months. She took them on time and is still bound to expire this coming January.

The thing is, last week (December 20) she had a 1 day mild spotting that we suspect should be due to the shot wearing off. The next day (December 21) she had nausea at the evening, but didn't throw up.

However, at December 28 (around 2am) she couldn't sleep and threw up several times, she claims she feels hot and thinks she has a fever, she has mild LBM, dizziness, and feeling chills. I am suspecting that she has the stomach flu. But she just threw up on that day and everyday since then she'd just feel nauseous and dizzy often at night time and she'd sleep A LOT.I'm wondering how likely that it is pregnancy symptoms? Or if she's just still weak from being sick?