See if you can find your hospital's covid policy online. At mine, you are asked to let them know if you have certain symptoms, or have tested positive, or have been in contact with a known case, so that they can take precautions, but they don't interrupt your treatment. Don't know if it's the same as yours but it'd be worthwhile to check.
Also consider that say a week's delay in your treatment might not make much difference, so if they did propose a short delay you could ask the oncology team / nurses about that. One of my oncs said to me "Chemo is a marathon not a sprint!" 😁 But my situation is likely very different, and of course every patient and exact course of treatment is individual so if it comes to that, just ask.
Right now you can let them know about your DD and then if you test positive or develop symptoms, let them know that as well. That lets them use extra PPE, isolate you from others or whatever they need to do to keep staff and patients protected if they do go ahead with your treatment on Friday.
Hugs and hope your daughter is well soon and that you don't get it after all!