goosteen, I'm glad to have found the knife connoisseur of the group! Thanks for these excellent recommendations.
Peter's boot method might be adapted for weaker footware with a small piece of sheet metal or wood.
In the videos of durian vendors in SE Asia I've seen on youtube, a variety of knives are used, from long, skinny kitchen knives to beefy short cleaver/machete sorts. I think there's a wide selection of beefy fixed handle knives on the market that would be fine for abusing a little. Two of the more unusual ones I've stumbled across:
https://www.aliexpress.com/store/product/Best-Gift-Home-Kitchen-Knife-Fruit-Durian-Knife-5c13-Blade-Rosewood-Handle-Camping-Fixed-Blade-Knives/819833_32806716337.html
https://www.lehmans.com/product/multi-purpose-power-knife/
Glad to be a service!
Those are both interesting, Off brands from Ali express are a little bit of a risk.... There's a chance the steel is not tempered correctly and it bends, or breaks, is too blunt, or can't hold an edge. But it does say 58RC hardness, but it does not mention the steel type. The shape could be good, it looks the flat top is for prying, and you could hammer the spine to get the thing into the durian. it's risky, but there's also a chance it works really well.
For me around the property, I find a folding knife with pocket clip is best, just because it's always on me like my keys. If I have to go get a knife, like a fixed blade, I find I rarely use it. Anything from Benchmade with the Axis lock is good. Since it's a gift you need, this could be good
http://customknife.benchmade.com/knives/#/customizer/blade ... Upload a photo of a durian to get engraved into the blade, Give her the mental edge over that fruit!
....When I do have to walk to the shop and get a knife, it's usually for a bigger task, so I grab the machete, Which in that case I recommend this one. Great edge, not too blunt, cuts fast and deep. ...If she's only opening the thing to get the seeds out, whacking it with this will be the fastest way!
https://www.amazon.com/dp/B00BNPV1RW/ref=twister_B014SK7GOA?_encoding=UTF8&th=1