hi there- i am not sure petunias care about very hot weather.
we had them growing in the cooler months in arizona, also the wind can "burn" them.
what i recomend is lantanas. they do very well in sunny areas, like hot, need little care. but she needs to put them inside in the winter. there are 2 types of lantanas- bush and ground covers. they both come in lovely colors, but the second could be used to cascade down.
hope this helps.

calibrocha "million bells" do better then normal petunias from what I have seen here and wave petunias too. Maybe some diascia. Possible trailing jasmine. Creeping Zinnia, verbena, maybe lobelia. Bacopa and nasturtiums. Really just have to try and see what works but those should do good with the sun and heat..not too sure about bacopa since I haven't tried that myself.

Has she considered flax seed flowers? I'm only just trying them myself for the first time but apparently they tolerant hot, dry conditions well and probably wind too. I don't think they'll cascade but they are red flowers with shiny green leaves and seem quite attractive. If the seeds aren't available down there, I know that Vesey's carries the seeds.

There is one kind of Petunia developed in Texas that loves the heat and takes off when all others fade, they're called Laura Bush Petunias. I think they're hard to find but I ordered a package of seeds for next to nothing and planted them outside in a milk jug with the wintersowing method (planted them in spring, though) and they got going with virtually no care! I am adding a link to the place that sells the seeds just in case. They come in purple or pink at this time.

Here is a link that might be useful: Wildseed Farms

Laura Bush Petunias are great but they do not cascade and they can get fairly large. I planted a few from seed for my school project. Now just 3 months later is about 20 inches high.

Also I forgot to mention phlox

I have a patio that has been getting super hot lately (probably about 90) - even full sun plants tend to shrivel. The petunias seem to love it. I even had a bunch of them piled up almost bare-rooted in a container for a few weeks because I bought too many, and they kept blooming. I did water them quite a bit though.

The sweet alyssum is doing very well in that hot spot too. It has tiny white flowers that are starting to cascade over the edge of the pot.

Also cosmos and zinnias, but I don't think those cascade.

How about a geranium vine? They will come back each year and they trial with flowers. They laugh at heat!

You'd need to bring them in during winter.

there 2 types of moss rose(portucula) the type you can grow from seed or is offered in paks during the spring tends to grow more clump-like. the newer choice is offered either in a hanging basket or individual pot. this one trails freely. the one problem is that in the evening when there is no sunlight/cloudy the flowers close up. good luck