It's just my impression, but it does seem that the RNG loves Peach, regardless of her being controlled by the AI or another player. Many stars spawn close to her, chance time makes everyone give her coins, she gets the best items, etc.
Me and my friends always feel like Waluigi gets favoured by the game.
I play Mario Party with 2 different groups of friends. With both groups Waluigi tends to win most often, and in the most ridiculous ways, even though those who play as him suck at the game.
Maybe it's just me, but it's always felt like Mario Party in general was rigged. To make it easier for the AI and worse for you, probably to make up for their zero intelligence/skill in mini games.
The only time I ever felt that an AI character was rigged was Daisy in Mario Party 9.
I couldn't even begin to tell me how often this character has absolutely destroyed me on most of the boards in the game because she got lucky that Bowser was helping her out, it's unbeliavable.
Ironically Magma Mine reverses this by making her the buttmonkey.
I'm not even kidding even if 4 characters particapete in the match it's always Daisy who get's hit by the lava, quite frankly I have seen this scenario happen to her:
in only a few matches that it would cover every single lava based board that came before it.
Other than that thought I never really feld like the AI was activly supported by the game, here is a very recent (yeterday to be exact) curb stomp victory of mine in Mario Party 3:
