You may need to "cook" up another "brew" to remove the cooking oil residue from the leaves. A little liquid dish detergent sprayed on the foliage, especially underneath and then washed off, should do the trick.
The oil may be plugging up the stomates (breathing pores) on the underside of the leaves. They allow moisture to be "pumped" from the roots, to evaporate upon contact with the air to keep the leaves cool. Being located in an 80° environment, they would need a lot of moisture to remain cool. Lacking that, they wilt!

After removing any oil residue, leave it outside in dappled shade, in an area protected from strong winter winds, you DO have those in the Phila area! (voice of experience)!

Since you live in an apartment, I assume you will be growing it in a pot. Not an ideal situation for Helleborus, but doable. Since they develop a huge roots mass, over time, you will need to step it into a larger pot, as the plant ages and multiplies.

As soon as it begins a new growth cycle this spring, I would move it into a larger pot. If now in a quart size, move to a nursery gallon (3 quarts), once the roots fill that, 2 gallons, next progression 10 quarts, etc.
Use a well draining potting mix (they hate wet, soggy soil), but it must be moist. Check the medium it is now growing in and try to replicate that.
They aren't a true xerophytic plant, but need watering only when the top 2-3" of the soil becomes dry.

Curious, which one of the Spring Promise Collection did you obtain? Link below.
Have yet to find any of them in my area. :The 2 nearest growers (VA), apparently don't service this market area.

Here is a link that might be useful: Helleborus Spring Promise Collection

I don't care what anyone tells you, hellebores are NOT indoor plants and should they need to be kept indoors, do so for the shortest time possible and under the coolest of conditions. 80F is far too warm (how can you tolerate that?? I'd die of the heat:-)) Depending on the size of the container, at that heat it can dry out very rapidly. These are very cold tolerant plants and can easily withstand freezing temperatures. If there are concerns about the plant being greenhouse grown, you can provide some protection with a cover at night, but it will be far happier out of doors than cooking in your apartment.

Now I've got that off my chest, very few aphids fly. It is far more likely that what you were seeing buzzing around was a fungus gnat - very common with indoor plants and generally associated with overwatering. Or possibly white fly. Even in the unlikely event it WAS an aphid, it will not bother the hellebore unless it was a specific species of aphid associated only with these plants. Hellebores are not overly appealing to common aphids as their foliage is too heavy/leathery to be attractive. And aphids do not kill plants unless they are present in overwhelmingly large numbers and then only with very young, vulnerable plants (seedlings). There may have been other issues with your orchids but their demise was not due to aphids.

I don't recommend homemade recipes as there is too much of a chance that improper proportions or mixing is involved and some plants will develop reactions to things like detergent. Best to use a labeled insecticidal soap (no detergents) sold for that purpose. And know exactly what you are treating for (correctly ID the problem) before applying any type of insecticide.

1) get your hellebore outdoors
2) investigate the possibility of fungus gnats or white flies on your indoor plants and treat accordingly.