Neighbors cat is terrorizing our cat!

We adopted a 2y-o female cat back last December and we live in a duplex apartment, where the direct neighbors have two cats. The female one (she’s a black cat so I’ll refer to her as that) is extra adventurous and likes to wander around, and has ended up in my rooftop terrace a few times. We have a cat net that covers the entire top of the terrace, making it really safe. However, the black cat has ended up on top of the net, terrorizing my cat because of course her turf was being invaded.

We also have our balconies connected, and the black cat used to spend a lot of time in our balcony before we got our cat, but since then we covered the bottom where she used to sneak in, although never let our cat out on the balcony. However, now that it’s very hot outside we open the balcony doors to let the air in. It was all good until a few days ago, when the black cat started sneaking in the balcony again through the fence. So I had the “brilliant” idea of getting a bamboo fence to wrap around the balcony so at least the black cat wouldn’t sneak in.
Then today I let our cat out for the first time and the black cat came and got too close to our side with a dominant behavior, so my cat climbed to the top of the fence really fast and if I hadn’t grabbed her, who knows if she’d have fallen out. I haven’t put a net in this balcony because it requires drilling and I’m renting. It’s just not ideal to use any of the other options without drilling, and made the mistake of thinking this bamboo fence would be enough. Also if I put the net from my side, the black cat would still get too close and my cat would felt threatened anyway.

So my issue here is, although I have also spoken to the neighbor many times, they don’t put any measures on their side and I don’t want to keep spending money on our side if it’s just thrown away because their cat always finds the way. Has any of you ever encountered a similar situation, and if so, what did you do?

PS: we are also thinking about getting a second cat to keep her company, but having seen her territorial behavior we are now hesitant. Any experiences?

Thanks a lot!