Would like if the actual incident was clipped. Because from using what she's saying and looking at the Twitch chat, it seems like a typical Twitch chat and in-line with what's expected on her channel.
Seemingly they wanted her bellybutton to show. Which might just as well be a call for a more faithful cosplay, as it can have had people trolling regarding showing more, to sexual creeps. However, there's also people in chat getting confused at her reaction, either people saying sorry that they were just trolling, people saying they thought trolling wasn't a big deal for her previously, people saying it's trolling gone wrong, etc. Seemingly it happened within the span of a minute, so might as well be a small group of intentional trolls raiding a streamer or it might an in-channel joke gone wrong.
Really, until a more relevant clip shows up, it's a pretty non-topic (actually it's still a non-topic, even if it does, because this is a reality for all streamers.). Yes, Twitch chat can often be terrible if you take everything seriously or if you're raided. It's not something unique though and generally there's a system of mods that help larger channels deal with stuff like this. According to chat the mods seemingly were sleeping. Or it was as I said somewhat within the internal humor of the channel, though not necessarily something she ultimately liked, thus causing mods not to intervene until they saw her reaction.
Streamers have to be prepared for the emotional tax, because they'll deal with a lot of positivity and negativity, a lot of wanted attention and unwanted attention. It's kind of like a stand-up set, you'll get hecklers. And unlike the heckler, you generally have an advantage, either in terms of your audience, in terms of being given the most attention to your response and argument or in terms of having ways of banning said person/people. Should uncomfortable experiences happen? Probably not. But if you've worked in most jobs, it's a reality. Work in school? You'll have a ton. Work in healthcare? Tons. Work in retail? Too many to think of.