Honestly, my biggest issue with Joyce was that at the beginning, she felt like a bit of a contrived obstacle. "Buffy wants to fight. Buffy's mother catches her. Buffy's mother threatens to ground her." It got annoying and I'd always fast forward through those scenes because I get it, parents just don't understand.
As far as being suspicious of Buffy goes though, she DID burn down a gym, or so Joyce thought. And, if you go by the episode in S6 where Buffy thinks she's insane, she apparently was put in a mental hospital for thinking she was the Slayer. (Although this may not have been established at that point. I kind of don't think it was, or else a lot of conversations in S1-3 would've gone much differently.) Either way, I do think she had good reasons. It was just... all very contrived to me.
no subject
As far as being suspicious of Buffy goes though, she DID burn down a gym, or so Joyce thought. And, if you go by the episode in S6 where Buffy thinks she's insane, she apparently was put in a mental hospital for thinking she was the Slayer. (Although this may not have been established at that point. I kind of don't think it was, or else a lot of conversations in S1-3 would've gone much differently.) Either way, I do think she had good reasons. It was just... all very contrived to me.