There are multiple different types of hemophilia with different underlying causes, but the two most common types, Hemophilia A and B, are both inherited in an X-linked recessive pattern.
A female patient with one normal X-chromosome and one bad X-chromosome would be considered a carrier of hemophilia (they are heterozygotes). To answer your question, it is important to recognize that X-chromosome inactivation (Barr body formation) takes place on the cellular level. This process occurs randomly and individually for each cell in the body. In other words, some cells will randomly choose to inactivate the X-chromosome with the good allele, and some will randomly choose to inactivate the X-chromosome with the diseased allele.
In the case of hemophilia (and many other X-linked recessive diseases), the cells that randomly choose to express the good allele generally produce enough working/functional protein such that the patient does not have symptoms of hemophilia. They are a hemophilia carrier but do not have hemophilia themselves.
