Interestingly, after finishing Arcane, I started liking Louise much more, and I realize that from her perspective Lena is kinda a shitty friend if you think about it because she never includes Louise in the fun unless she's dating Jeremy. I can't imagine how lonely and abandoned she must feel whenever Lena goes to have fun with girls, or has another date with Ian, etc, but Louise has to stay at home with the person she despises. Granted, I don't think she's fair to Stan, because he only acted inappropriately with Lena's encouragement and lack of personal boundaries. With Louise, he simply wouldn't dare to be a perv. But it's besides the point because Louise didn't spend enough time with him to trust him so it's still stressful for her. I know to Lena it might seem that Louise is overly needy, but had she spent some time with her when she's free, maybe Louise wouldn't complain that Lena prefers spending time with every other person in her life but never thinks about her. I'm actually surprised that Louise has taken so long to explode with frustration. Lena can show support for Stan who feels shy being around his flatmates. Likewise, it would be very nice of her to check up on Louise from time to time and also take her whenever she goes out to have fun with someone. Or hell, they live together, plenty of opportunities to do something without even going anywhere.
That said, I agree with Echbert who said that it would be good if we were shown more often Louise's positive sides instead of needy, jealous and judgmental ones. As of now, whenever Lena can rely on Louise, she acts very clueless and doesn't know how to deal with anything which makes us think that she's not the best person to come for advice. But even if she doesn't have a lot of wisdom, she might have her strengths. They have the potential to be as close as sisters if Lena didn't act like an inconsiderate cold bitch half the time.