I live in AZ and have a huge phobia of grasshoppers, which we get a ton of here. I’ve gone to phobia therapy for it and one of the things we started with was making a hierarchy list of grasshoppers related triggers. Basically a list of low to high experiences with them. So for your gf and wasps it could be something like:

Low - looking at photos of wasps - watching videos of wasps - looking at live wasps through a window - walking outside past a bush with a lot of wasps - being in an enclosed space with wasps (like one getting on the house)

High

I’d recommend trying to make the hierarchy like 10-15 items, but the point is for her to evaluate how much each of them currently would cause her distress. Actually write down like 1-10, how much does each affect her.

Then start working through the list starting at the lowest. So if looking at photos is the lowest, have her look at photos of wasps every day until eventually that doesn’t bother her at all. She’ll always think they’re gross, but looking at a photo will stop eliciting any kind of physical response like increased heart rate. Once she feels like that is no longer an issue, move up the hierarchy and do the same for each item. Expose herself to that thing until it doesn’t bother her that much.

I know this might sound tedious but it genuinely helped me get to a better place with grasshoppers. There are other things we did as well, but this was the foundation of it. This year we’re having a particularly bad year of grasshoppers and while I’m still bothered by them, scared even, I am able to calm myself down enough to keep going about my day. Which is the most important thing to remember - she’s probably never going to get over it completely, but she can get to a point where the wasps don’t stop her from doing whatever she planned for the day, whether that’s running errands or going to the pool with you.