PP have linked to the correct document Managing Medical Conditions in School.
DD needs an Individual Health Care Plan, which it sounds like she has but it perhaps needs updating. (This is not an EHCP, which would only be relevant if DD also has additional learning needs or requires significant adaptations to be able to access school that would cost over the nominal first £6000 that schools have to fund.)
Providing wipes, if DD can manage them, is not unreasonable. Not so much for her desk and chair, which you coukd request are used by her alone, but for the shared resources. Providing pencils etc for her own use is a good start, but there will be other items that are shared in the classroom, such as practical maths or science resources, that would be easier to wipe down than to ask you to provide ready for a specific lesson.
What else would be reasonable to ask for depends on the school's context and staffing. To be close to a window, to only attend lessons in her classroom, ie not to attend assemblies or to change rooms to be in a certain maths set, to keep her coat on her chair rather than in the cloakroom, to use the disabled toilet, for you to be informed if certain illnesses are identified in her class.
It might also be worth discussing the option of a part-time timetable if DD's doctors consider that she is at greater risk of picking up something if she is tired and becomes rundown. You will probably fall the wrong side of the attendance data computer software sooner or later, and whoever does the admin for that should know to override the automatic letters. If you are contacted, take it as what it is, that the school fulfilling its duty to check that everything is ok, and meet with them to tell them whether or not everything is currently going well.
The headteacher is basically correct that it is impossible to stop all germs spreading in school. You said you spoke to them that morning, but was this a pre-arranged meeting where they had had DD's relevant information beforehand, or did you just catch them on the playground at drop-off, potentially just one of many parents they deal with every morning with, what in most cases is a simple or trivial question?
The headteacher's wording was clumsy but they probably didn’t understand the seriousness of DD's condition. Try again with the Senco or whoever updates the IHCP with you. You could ask DD's consultant to copy school into their reports. Then the school always has first-hand exactly what the current situation is, and the medical evidence for updating the IHCP, without you needing to remember to send it in after every hospital visit.