I have an Explosive Child, I've read the book, which saved us, and that inflexible personality fits my 8 year old perfectly. When she is in that frustrated mode, there is nothing you can do to please her. She's just mad. She needs to learn how to fix the problem herself. At explosion point, all they want to do is fight. Here's what I would do. When she is calm and happy, tell her you are going to teach her how to make her own milk, so she can control herself exactly how warm it is. Then walk her through the steps, having her do it herself. Make sure the milk and microwave are kept within easy access for her. Tell if she asks you politely, you will remind her how by talking her through it, but you will not do it for her. Tell her another option is to drink it cold like most all kids her own age do, or to drink water, which may be quicker for her to get. Be prepared for the mother of all tantrums the first time she begs, pleads, and demands you do it for her. Don't give in. And keep doing what you're doing by having her clean up her own messes, that's a good natural consequence. If you don't give in, she'll either start doing it herself without a fuss, or give it up.
I had to go cold turkey on my child for selecting clothes for school (she's responsible now to do it herself) and tying shoes (she can do it, but used to prefer them being tighter like used to do for her). Cold turkey can and does work well, if you explain it when they are calm, and don't give in! During your calm talk, you can also ask her to help come up with some ideas. Emphasize that you are concerned, because you see how stressful this is for her, and you don't want to see her go through such sadness and frustration. You are going to help her because you care about her and don't want to see her so upset when she doesn't have to be. Good luck!