Who Is Legally Obligated To Pay For Bed Bug Treatment?

So background, I know 100% I have bed bugs. I live in a townhome, and my neighbor just received treatment in November. They have now crawled through the walls into our side. I’ve lived here for 3 years almost, and she was telling me she has had them since 2020. The exterminator our LL hired specifically, and documented on their quote, recommended treatment for both sides. Never made us aware of this problem. I warned the neighbor and she is the one who told me she has had them since 2020. He made her pay for half the treatment. Now that they’re on my side, can my LL require I pay half? He was warned this would happen and ignored the professional. I personally don’t feel like I should be required to pay anything. He rented me this house fully knowing of the problem next door. I refuse to live with them for 4 years myself, so if he doesn’t get proactive with it, I will do the option of crossfire, so long as it won’t trigger my asthma. I’m in Pennsylvania. Thank you. Also want to say, if it comes down to I have no choice but to pay half, I will do so to be free of the problem. I just don’t feel I should have to, or really want to when I already pay $2200 in rent for a comfortable living space.