Lily, 

The agreement is with the gender of the speaker as the direct object ‘me’ in “m’a vraiment aidée ” precedes the compound verb and the speaker is female.

 By the way, it is helpful if you include the full sentence/context when querying content like this as it saves needing to find the specific example before replying.  

 Special cases when the past participle agrees (in number & gender) when used with 'avoir' in the compound past in French (Le Passé Composé)