I feel like it's not a stretch for someone who already knows how sloppy she is to figure she'd buy a low-maintenance potted plant.
Here is an alternate take:
She bought a cactus because she knows she's a lazy slob that would forget to water her plants regularly.
Then she did indeed neglect her cactus ...yet it died from over-watering.
Rather than filming her, her stalker is sneaking in to water her plants!
Or maybe she did water it, but her stalker 'friend' assumed she wouldn't and took it upon himself to care for it - so it was getting 2x the required amount.