Case 1: ...Spent whole day texting each other, talking about families, relationship, etc...

Case 2: ...she would start and maintain long conversations about everything, trying to make jokes, asking me stuff, etc...

There's the problem brother. You have successfully friend zoned yourself. You were an easy kill.

sexually unavailable,

also flaking is not really a big deal, but as soon as you notice it in a pattern, it is a good sign there is dis-interest, a girl who is not compliant is a waste of time, you should pay attention to compliance more then indicators of interest, what she does is far more important than what she says

even if a girl finds you attractive, there are alot of other circumstances that will determine if she is sexually available to you, not only that but if she doesn't feel like she is comfortable with you or has some sort of connection, she is less likely to feel like meeting up (this is more of an issue for cold approaches, if you have a good couple hours of face time, this problem is most likely solved and if you are getting flakes it is another issue)

...For Case2, I'm not sure how things could have gone differently though since we work together and she also has a bf so wouldn't I need longer contact in order to build more attraction for something to happen?

Hmm... so what does it mean when there is compliance in the beginning and then flakiness and non-compliance all of a sudden? To the point of hardly saying good morning let alone making a conversation? And yet, when we're with a group and I tell jokes, etc, I will catch her looking at me smiling at different times, like after I've finished talking or when someone else is saying something, or when there are random pauses. Then again she doesn't have much choice because everyone else at work is boring as hell...

I wonder if I should have just done more to maintain the feeling of attraction in the days between setting up the meeting/date and the weekend. In that she was at an emotional high when I invited her and then my acting cool and casual let the feeling dwindle over the course of the next few days.

Thanks for your input!

she used to meet up with you on dates before, one on one without her boyfriend?
were you kissing her?, was there meaningful kino established?
was she well aware of your sexual intentions while offering compliance?

Proximity alone or your nearness to her can build sexual attraction. It has something to do with male hormones. Crank those sex hormones up and you don't need to talk much. Talking too much = Friend; Talking less but more action = Lover

Sexual Attraction Multipliers

• 1. Sexual innuendo
  
  2. High hormonal levels triggered through exercise, excitement due to accomplishments, or watching a violent movie.
  
  3. Kino escalation or Kino pinging
  
  4. Display of dominance and sexual intent through eye contact
  
  5. Intrusive thinking. Don't answer her questions directly. Let her want to know more about you. Don't tell your age, your name, number and so on. Let girls work hard for these information about you. When she thinks of you more, the more attracted she will become. If you leave her with nothing to think about, you lose.

Sexual Attraction Destroyers

• 1. Opposite of items above.
  
  2. Being an easy kill. Make her chase. Make it hard for her. When you do reward her, it will be the sweetest reward for her even though your reward is just SPAM your phone number. She'll jump up and down gleefully.