Here's what I do know, not sure about other countries, but in US some events, like weddings, could be HUGELY expensive. Hiring a DJ for one evening alone is typically in thousands. Corporate events are usually held in commercial venues and the venue will provide the PA and other A/V stuff.
I feel like your sister needs to reconsider for now A/V equipment renting until it's worth the investment and her business could sustain (and profit) for investment in Pro A/V gear.
Unfortunately, None of the links you've posted would worth spending money on, since none of them are good quality in neither sound or build.
This is the cheapest compact PA with the BT system which I'd consider at 3x your budget:
https://www.amazon.com/Yamaha-STAGEPAS-400BT-Portable-Bluetooth/dp/B07B679W4K
If you click to call, they likely to give 10 to 15% discount