Insiders revolting against a friend's visit

I planned for a friend to come stay at my house for a couple nights so she could get out of her house and have some relaxation. I know she won't be able to sleep on the couch so I also offered her my bed. I should never have offered her either. I'm okay with it, but some of my parts are not having it. Offering her the bed is simply not okay. It's time for me to pick her up and I feel so sick I haven't been able to do anything to clean up the house at all. I have a migraine, nausea, and dizziness so bad all I can do is sit. I don't know how to tell my friend I need to cancel, especially since I know she has her own issues with trust and being let down. Insider negotiation is simply not happening. Any advice or encouragement would be much appreciated.

I think its okay to be honest. You had pure intentions, you wanted to help out your friend an offer her some respite by the sound of it. But in the end it might only make things more stressful for your friend if on top of whatever is going on for her she then fins herself facing less than happy insiders who are stressed out by having her there.
Can you offer her some fun evening time together (or whatever it is she needs) but explain that the situation is best if she doesn't stay after all? (With as much explanation as you feel comfortable with)

Thank you, Amyjay. You're right. I texted my t and she said I'm honestly sick and I just need to tell my friend that. Of course I feel guilty because as soon as I cancelled I fell asleep for a couple hours and then felt fine. I told her I'd make it up to her. We will spend the day together tomorrow but I'm not going to offer her to stay the night. I should have discussed it inside before I made her that offer in the first place. It's a lesson learned. My t is always reminding me to check inside and make decisions with my the others instead of for them, as much as possible.
It wouldn't be good if she stayed over because I'm sure some of us would have been mean to her or otherwise alter my behavior around her. That was a good point you made. I sort of wish I could explain it to her but she's not someone who would be able to understand, and she has the habit of telling other people's business to those close to her, which wouldn't be good at all. She's been my friend for years and I have a feeling of responsibility toward her. She needs help in life, and can be draining, but she can't see that and doesn't have the ability to change that about herself. She also wants to be closer to me but I maintain a distance for all these reasons and more. More than anything I wish she could accept, somehow, that I just can't be the best friend she wants me to be.

Wow good on you for doing what you needed to do. it sounds like you are doing all the things you need to do to take care of yourself and set appropriate boundaries in this friendship (and learning about appropriate boundaries inside too).
I am a bit like you I tend to make decisions without consulting inside and it does backfire sometimes. My new t has asked me a couple times already are all the parts inside okay with that and I am like "I don't know, what does that matter?" Guess I have some learning to do of my own in that regard.