Since I love Prue to bits, I'm gonna have to stick up for her on this one.
Firstly, yes, I agree that Phoebe's character had more of a storyline at that point with the Cole thing. But even if Phoebe did die, they could've made it work. It wouldn't have gone down the same way, but they would have found a way to keep Julian in the show.
Yes, Prue didn't have much of a life but can you blame her? She did have to protect her sisters. It wasn't like before they were witches where they were both old enough to take care of themselves. Once they became witches, everything changed. Every little thing that happened in their lives was potentially life or death. You can't expect Prue to just switch off her maternal instincts and say "they'll be fine, they can handle it". It all stems from her childhood. She protects her sisters because she doesn't know anything else. She can't separate her sisters from her own life because they are her life. Personally, I find that rather admirable.
And I wouldn't say Prue blamed her sisters for having fun in their lives, it's just that she wanted them to moderate it. Before Season 1, Phoebe was off having fun in New York. Then she lost her job, had no money and nowhere to live etc.., who did she turn to? Her sisters. Had Prue or Piper been different people to who they were, they probably wouldn't have cared about her. But when Phoebe needed them after going overboard with the fun, they were there. Prue's problem wasn't that they had fun, her problem was that they could NEVER shy away from their responsibilities and from who they were. It didn't matter if Phoebe wanted to party the night away, get wasted etc...she couldn't. Not because Prue said so, but because her destiny did. As a Charmed One, Phoebe has a responsibility to all the innocents out there, Prue just reminded her of that. It wasn't about "just because I can't have fun, she can't" - it was Prue looking at the bigger picture. And I'm glad there was always someone to do that. Had Piper and Prue never been around, you can bet your a$$ Phoebe and Paige would no way have lived up to their responsibilities to such a huge extent.
I will not add more. Ur thoughts are clear and awesome. Love every sentence u wrote here.