Check with your local community government regarding ordances which require control of noxious plants; also contact your State forestry or wildlife department. I understand that Japanese Knotweed is on the PA list of invasive weeds. Your neighborhood may not have a specific regulation which would apply, but it would probably be worthwhile to contact a Pennsylvania law school or university to learn if there are state laws governing the knotweed invasion. I'm not a PA resident and not familiar with PA laws or regs, however I would consider it unlikely for you to be breaking any sort of regulation by removing the plant's branches and/or roots from your property, but there may be some regulation that would require the neighbor to keep the JK under control.

I strongly suggest that you do NOT apply salt to your soil as it can take many years to rinse sufficiently for *any* plant to grow, and [of course] the salt will leach and re-distribute whenever it rains, snows, or is irrigated, which will increase the potential dead area.

Here is a link that might be useful: Japanese knotweed

Try spraying it with a strong solution of Roundup.

control of Jap knotweed is difficult. I mistakenly planted it, wow. I've tried cutting it to 6" and applying round up down & on the open shaft and on the remaining leaves, it kept sprouting. The only other method is to pull out the runners, and in my sand they came out quite easily, and are gone in that area now. They do look quite wonderful in the fall when they flower, maybe that is why your neighbor likes them. If she is considerate and understands your problem, maybe the two of you could pull out all the roots. She probably will not do anything if you don't talk to her, especially in a nice way-mention all the bees that are attracted in the fall and you are afraid of getting stung, plus the driving situation. You will probably have to do most of the work yourself. I know if a neighbor wanted me to change my yard to suit them-and I didn't care-the neighbor would be doing all the work not me.