it is possible for the cooperating party (b) to be aware of in-fill relationship status and continue in relationship. however, most instances of such are due to a total lack of dignity as well as a willingness to accept whatever conditions and requisites said relationship has, regardless.
it is also possible, however rare, to be involved in a double in-fill relationship. this is not to be confused with a fuck buddy. whereas an in-fill relationship not only has all of the appearances, but does in fact exercise, the majority of activities of a real relationship.
"looked real to me."
"it sure felt real..."