This was bugging me a lot, because it seems like it should be relatively easy, given that they have those wide open showers and you can see slight slips of the nips in those clips. I found this archive:
https://videobrother.net/sub_pages/archives_au
And watched through the "uncut episodes." You can see boobs from a lot of the house guests... all very briefly. Honestly Bella looks really similar to the other brunettes on the show, so I couldn't always tell the difference between them. It's honestly ridiculous how hard it is for me to tell some of them apart as I casually scrolled through. Felt like I had face blindness. But I think...
S15 E12 @ 12:45 - Side profile nudity. She's covering her nipples with her hands.
S15 E18b - @ :50 there is VERY brief shot of what might be her topless although the quality isn't great. It seems like they're out in the yard playing a game, but I have no idea when that happens as it's nowhere else in the episode. This is also the episode where the original linked clip is from. You can briefly see her nip right before the scene transition.
I never found where the screenshot to the privated video from the other site was from. I also only checked the "uncut" episodes. I'd like to see if there's more context somewhere to when she's standing out topless while the dudes are wrestling, but I'm done searching. If somebody else wants to take up the cause, I'd be happy to let you.