Yes, I understand what you're saying, and yes, I would like to see that too, but a lot of what you say is also wrong. It's not the writers' job to have Jaye and Mallory develop feelings for each other. You're putting your ideas into the heads of the creators. They had a different idea to yours, it doesn't make it the wrong one, it's just not the one that you (or admittedly the majority, it seems) wanted to see. Ultimately, what you wanted doesn't fit the personality they crafted for Jaye and/or Mallory, and it wouldn't feel right for them to shoehorn in a relationship that didn't fit. I can understand that, and I can clearly see the reasoning in the dialogue throughout the game, but in particular in the last episode or two. A lot of what you seem annoyed at here looks like it is based on how you would have reacted in the shoes of various characters, but they are not like you, so they are going to react differently.
With regards to bisexuality, Jaye clearly gives notice of her thoughts on a couple of occasions. She is not interested. She may have tested the waters with Tara when she was younger (although it wasn't exactly in a romance/relationship way), but that doesn't mean her sexuality will be the same now as it was then. Things change, people develop. To borrow from a popular phrase, people do, in fact, sometimes go back after trying black. My wife used to be a vegetarian, but she isn't anymore. It would be wrong to call her a vegetarian now, as she's changed. Although I never would belittle her decisions this way, you could say it was just a phase she was going through. It's the same with a lot of women saying they "experimented" in their younger years. It doesn't mean they are bisexual, just that they once had a taste of it.