I think there are two different issues regarding rationing health care, within our society (I am not talking of people living in sub-Saharan Africa, but people within our communities)
One is about what level of treatment should be covered. This is decided by NICE and it applies to all. If we won't provide controversial/expensive drugs to A, we won't provide them to B or anyone else. This is not discriminatory, it is applicable to everyone. Btw, this is done everywhere, even in private insurance, and is based on cost-effectiveness clinical metrics and evidence
The second type of rationing is about discrimination. It says that X members living in our communities will get healthcare coverage, but not Y. And therein we go down a slippery slope. In 1981, a sick child like this baby girl, would have been treated by NHS, but not now. In the near future, we might pass a law saying that people who are on benefits can only get limited access to care, or only for the first two children, because, you know, resources are not unlimited. And the after, we will further restrict it to people who pay in only getting any access to care, because we lost all compassion for others and judge them unworthy and parasites.
The minute you give up the moral argument that all the vulnerable living within our communities should be cared for, you start by eroding benefits for everyone. Whether you realise it or not, your pointing fingers at this child will one day mean that people will find probably find you unworthy of care and your children a drain on our system. And then pass a rule to that effect
For a welfare state to be sustained, we have to protect the rights of the most vulnerable, not exclude them. Because once we exclude some people within our society, anyone else can be excluded too, based on the political hot-button of the day.
That is why it is better to ration care for everyone. Have everyone pay a bit for care, if need be, rather than be greedy and just want all the possible freebies for only some groups. Because there is no moral justification for that.