When you upset the Mistress of the Dark herself, you might find yourself in some pretty hot water -- which Ariana Grande may be learning all about after some heated accusations about her behavior at other people's shows.Over the weekend, Cassandra Peterson aka Elvira made an appearance at Knotts Berry Farms seasonal Halloween event, Knotts Scary Farm.While participating in a Q&A during the appearance, she was asked to detail some of her experiences meeting celebrities. When someone in the audience shouted Ariana Grande, Elvira laughed as she called out some of Grandes shocking behavior.See on InstagramShe [Grande] came [to a show] and she brought 20 guests, said Elvira, adding the total ticket count came to 21 with Grandes inclusion.Adhering to the request, Elvira said Grande came backstage, then further asked if I could take pictures with all of her friends and relatives she brought.Elvira went along with it again and took a picture with every single one of them. I sign autographs for every single one of them.Once Elvira wrapped up her autographs and photos, she said she asked Grande if they could also have a photo, to which Grande allegedly responded, No, I dont really do that.See on InstagramAfter an audible gasp and boos from the audience, Elvira added that Grande also added salt to the wound by leaving the show before it started -- though her 20 guests stayed behind to enjoy it. Of course, the story has gathered many opinions, with some affirming there was no way Grande, whos slated to play the good witch Glenda in the upcoming fim adaptation of Wicked, could be so rude. Others have Peterson's back in the matter and appreciate how she called out the celebrity diva.Check out the clip to decide for yourself if Elviras telling the truth, and keep scrolling for some of our favorite comments either way.@elviraisqueenElvira, living legend, describes her worst celebrity encounter. #arianagrande #elvira #elviramistressofthedark #cassandrapeterson #scaryfarm #halloween #teatime #hollywood #knottsscaryfarm (@) (@) (@) (@) (@) (@) (@) (@) (@) (@) (@) (@) (@) (@)