IMO diamond cut alloys are more trouble than they’re worth;
- the diamond cut lacquered finish suffers from poor durability, specially during the winter months when the roads are salted.
- diamond cut alloys almost always succumb to white worm corrosion - usually when they’re between 2 and 3 years old.
- they’re more expensive to refurbish than painted / powder coated alloys, and can usually only be refurbished a maximum of twice.
- they’re easily damaged by inexperienced tyre fitters or poorly maintained tyre changing equipment.
Those alloy wheel protectors such as Alloygators aren’t usually recommended for use on diamond cut alloys; if dirt and grit gets between the wheel protector and the lacquered face of the wheel, the lacquer can get damaged, water then gets under the lacquer and you get the onset of white worm corrosion.
With any car I’ve had with diamond cut wheels, I’ve swapped them for a more durable set of painted / powder coated alloys.
@Steve309; if your car’s in good condition, I’d avoid putting ‘any old thing’ on it - I’d want a set of wheels that suit the car, look good and (if buying a used set) are in good condition. There’s always a risk attached to buying used alloys as you don’t know the history of them. They may have suffered from cracks or buckling and been badly repaired. If your budget doesn’t stretch to buying a set of new wheels, always make sure you ask the seller if they’ve ever suffered any structural damage, what the damage was and who repaired them (you can then check out the repairer’s website to see if they actually do structural repairs - some reputable alloy wheel refurb companies won’t, on the grounds of safety).
With used alloys - or new for that matter - I’d avoid cheap Chinese replica alloys as they may have structural quality issues and the finish may be poor. Also, they may not have been subjected to the same degree of safety testing as alloys made by well known reputable wheel manufacturers. I’d always try to stick to OEM alloys as they’ll bolt straight on and you can use existing bolts - assuming they’re the correct size and offset. Alternatively, if considering aftermarket wheels, I’d stick to a well known reputable brand; e.g. Borbet, BBS, Ronal, Oz etc. Always ask the seller to let you see the reverse side of the wheels to check out the details that are stamped into the spokes - e.g. manufacturers details, size / offset details, safety testing mark (TUV, JWL, ABE or equivalent) etc.
Almost everyone is likely to experience the misfortune of damaging a wheel at sometime during their driving life. Would some refresher training on parking / judging the car’s size and distance from the kerb be useful for your wife? It would help to keep your wheel refurb / replacement costs under control.