Avoir or être

Question

If reflexive verbs always use the auxiliary verb 'etre', why is it 'Quand elle m'a embrassé' and not 'Quand elle m'est embrassé'

Accepted Answer

Esther, 
this is not the reflexive (pronominal) verb " s'embrasser ", but the standard verb " embrasser ' preceded by the direct object ' me ", with the subject being 'elle'. ‘Embrasser’ conjugates in compound tenses with ‘avoir’. 
In other words, this is not a reciprocal action. In English, this is "she kissed me" ( and 'me' is male, as determined by the French past participle ), not "we kissed each other". 
The reciprocal statement in French, requiring the pronominal, would be " on s'est embrassés " or ' nous nous sommes embrassés ' - 'we kissed each other'.
Difficult I know, but a number of verbs can be in standard or pronominal form, and the context and conjugation of the verb both convey information.
 https://progress.lawlessfrench.com/revision/glossary/voice/la-voix-pronominale 
https://www.larousse.fr/dictionnaires/francais/embrasser/28656
https://www.wordreference.com/fren/embrasser