I hate to be a wet blanket for your first post, but is your sister in a location where this apple is likely to do well? I'd hate to see you work so hard to find her her namesake, and then have it be nothing but trouble. Here's the orangepippin site's description, for those who have not already looked for it. It's way too new to be in the public domain yet, so you're not legally going to be able to get scions. Rootstock would not be useful and you would not find it.

The original description doesn't sound all that wonderful, but the comments following it suggest it's better than first described.

I hate to be a wet blanket also, but I think it might be very difficult or almost impossible to get an Ariane tree here in the US anytime in the next decade! I went through something similar looking for Taylor's Gold pear scionwood, another fairly newly introduced variety; and after much searching I at least was able to buy a tree from one of the 3 licensed propagators here in the US - but scionwood isn't available, anyone that gets a tree signs a non-propagation agreement....so though there are 200 trees only 20 miles from me, they couldn't let me have any scionwood! Since the people that developed the pear want to make back the money they spent, it's patented; and the Ariane apple's website says "Created, developed and grown exclusively in France"; so I'd think they aren't planning on exporting anything except the fruit! So the only way to get scionwood would be to smuggle some in from France! And pretty sure that importing a living tree would be very difficult or impossible, with the quarantine involved.

At least the Taylor's Gold was being licensed in the US, but it sounds like there's no plans to do anything like that soon for the Ariane. I'd also wonder if it would survive much less thrive in Minnesota, most of France is a lot milder climate very similar to western Oregon. I'm sure that in 10 or 15 years when the variety has been well propagated, it might be more widely available......
Dave