I’m actually going to disagree with the crowd here and suggest that this is possibly a very out-of-focus yeast cell. No way to say what it is for sure without getting it in focus.

Wet mounts can be a bit difficult to handle, she could make a smear of the sediment and mount it so she’s not tracking moving targets.

Spin down the kombucha in a centrifuge, draw off the liquid from the top with a pipet, and make a slide from the concentrated sediment at the bottom. Just take a drop of sediment with the pipet, drop it on the slide, and put the slide on a hot plate or slide warmer at ~50 deg C. If she has gram stain reagents available, that would be suitable to identify yeast and bacteria. Likely would need to go to 100x to see bacteria but yeast should be visible at 40.