The phrase is 'bat mitzvah'. Bat mitzvah, which means 'daughter of mitzvah' is what a Jewish girl is called on her 12th birthday. This means that she is considered ready to take on the religious responsibilities of a Jewish adult. This is often accompanied by a religious ceremony that is referred to as the bat mitzvah ceremony.
Note: This is an americanism that doesn't translate literally into Hebrew. You don't actually have a bat mitzvah. You become a bat mitzvah, or you have a party in honor of becoming a bat mitzvah. I hope you have a good bat mitzvah (party) = a male says: ani mekaveh sheyihyeh lach (mesibat) bat mitzvah tovah אני מקווה שיהיה לך (מסיבת) בת מצוה טובה a female says: ani mekavah sheyihyeh lach (mesibat) bat mitzvah tovah…
Your friend has a bat-mitzvah and you are supposed to write her a letter you havent seen her for a while what and you cant come to her bat-mitzvah what should you write?
Congratulate her on her Bat mitzvah and tell her you know she did a good job on the bema. Tell her you have been thinking of her but can't make it to the bat mitzvah and that you are sending a small gift. You could find a picture of the two of you and frame it or give her a nice necklace to remind her of your friendship and her bat mitzvah.