Xander was the opposite of a good friend to Buffy here. A good friend would ask her first if she is ready to talk to him and then ask for her perspective, since it is, you know, about her relationship. Instead, he came with an already formed, biased opinion and patronizing attitude. Like, I'm sorry, but if even my best friend talked to me like that when I'm already justifiably pissed, I would not have replied in a nice way.
The same with Riley's ultimatum. If I was in Buffy's place here, even if I was inclined to give Riley a second chance (not likely, but let's pretend for a moment), if