This claim is false. It doesn't seem that she had a meltdown during her speech. According to Merriam-Webster, a meltdown is a rapid or disastrous decline or collapse, which is not what happened in the video clip you provided. She just seemed very passionate about the topic she was fighting for. In a different post from Fox News, it seems they labeled her speech as emotional rather than a meltdown, which is a bit more accurate than having a meltdown. I would not go as far as to say she was being emotional, but she seemed she was just trying to get through to her audience. Considering all the flack she got online, it seems that no one on the internet understands what a meltdown is either. Even if someone is ill-informed or using incorrect stances to defend her own, if they are speaking in the same tone she did, they would not be having a meltdown, they would just be passionate about their stance. Just because she belongs to certain political parties does not mean her words are more or less part of a meltdown.
https://www.foxnews.com/video/6321437618112