The dislocated relation is used to analyze detached elements that do not enter in the core grammatical relations of a sentence.
Hint
This relation can also be used for pronouns which are detached from the core syntactic structure of an utterance, such as French tonic pronouns.
In case of multiple propositions in one sentence, dislocated is used when the second proposition doesn’t hold any actual information value and it cannot be neither separated nor negated.
In this sentence, the proposition J’ai des copines (I have some friends) doesn’t provide any information. The fact that the speaker has some friends is considered as obvious and we cannot negate it or question it. The informational content of this sentence is about these friends, not about the fact that the speaker has some.