My friend is "mon amie" and not "ma amie", even though "amie" is female. This is because the French dislike having a word end with a vowel and the next one begin with a vowel. This overrides the usual gender system.
Unsurprisingly, this applies to other feminine nouns that start with vowels, too, like "mon échelle" (my ladder). I find that this means if I'm trying to remember the gender of a word like this, it's usually best to try and remember the indefinite article that goes with it (un/une) rather than mon/ma (which might not match) or le/la (which change to l' before the vowel).
I remember this first came out in the occupation lesson. My lawyer is "mon avocate" even though "avocate" means female lawyer.
so, how do you differ the gender? is there a way, like in english, to say "female lawyer"?