When I look at the two sentences below how can I tell straight away whether they are a reflexive action or a reciprocal action as they both have 'se' in the sentence:
Elles se maquillent
Elles se parlent
You need to look at the meanings of the verbs.
Elles se maquillent : reflexive because we assume each girl is making herself up.
Obviously context is important, but to change from reciprocal to reflexive (or vice versa) we'd usually have something to give that context.