It seems a little odd they'd add this perk but for only regular gas and not premium but then, the perk is an unusual one to begin with. Can she fill up anywhere or is this from some captive pump at her job site? If it's anywhere, it might be worth it for her to contact HR and ask some more about this benefit indicating her vehicle recommends the use of premium and whether they can consider allowing them to use premium even if it's only paid at 90% or something. Sometimes companies come up with things like this but it's decided by people who have no clue of such things as premium fuel being recommended for particular vehicles. A little education and requests might help them expand this.
The owner's manual states it's okay to run 87 octane albeit at a lower performance level. It does not state that damage will occur or not to ever run it. There have been long threads here debating the use of lower vs higher octane with people having their own unsubstantiated opinions, but I stick with what the manual recommends - premium, but I'd feel comfortable that I could put 87 in it if I felt like it and didn't care about performance (but I 'do' care about performance).
You'd still have the option to use 87 normally and then put in premium when you know you'll be travelling in the mountains, etc.
$50/week is $215/month which is a lot of money to discount without having a legitimate manufacturer confirmed reason not to do it or a desire for the most performance possible on a daily basis.
Another relevant point - depending on your mileage, you may have a lot more warranty left on the vehicle and depending on whether you plan to keep this for the very long term or just a couple more years may influence your decision if you have any concerns about damage to the engine, even though the owner's manual doesn't indicate that'll happen (assuming you don't notice any knocking, etc.).
