The detail is slightly complicated and very boring so bear with me!
Background- Friend and I are in a choir together. I've not known her long, just under a year, but I really like her. Choir employs a conductor. He can be horribly shouty and rude. Trying to broach this with him has never gone down well. (understatement) .He is a very volatile character.
Friend is getting involved in a romance of sorts with him.
At our last performance I made a mistake and came in early on a song. About ten other members (around a third to half the group) also came in at the same time- I thought the conductor had cued us in. I do find his conducting hard to follow at times and others have mentioned this as an issue, including some comments this time from the (professional) soloists.
Problem- I'm on the choir committee, and my friend has just become the new Chair. I brought up the conductor, asking if there was a way we could talk to him (without him getting v annoyed) about giving simpler signals . I mentioned the issue with the song. Friend then snappily said "they should have bothered to learn their music and then there wouldn't have been a problem" I was a bit shocked at both the comment and the tone of voice, and as I was obviously included in the "they" I replied that I had learnt the song . She then said, even more loudly and sarcastically "well obviously not, or you wouldn't have come in at the wrong time".
This was in front of the committee.
Everyone made some mistakes here and there in the concert, including friend. I don't have any problem at all saying "oh bloody hell i messed up those three bars" or whatever, we are not a professional choir. I am only learning to read music, and I still learn by ear, so I work really hard at home on my part. This time, unusually, we sang without sheet-music and I think I made less mistakes than the average member because I am used to not relying on the sheet.
I am really upset and offended. She basically accused me of not bothering to learn my piece, and then blaming the mistake on the conductor. And she said this to the whole committee.
She sent an email the next morning asking if she'd upset me. I replied "yes" and why. She then denied saying it at all. 
. I replied with what she'd said and explained why it had offended me, and that I was particularly upset that she would speak to me in this humiliating way. She has responded with an "I'm only human and that wasn't what I meant at all" sort of message. So how to proceed? I'm even wondering if I really want to stay in the choir, as with the shouty conductor and now this issue, it is turning into loads of stress rather than fun. I don't understand why she was so rude to me. We are all polite to each other on the committee, even when we disagree. We do have some members who make a lot of mistakes, or don't learn their parts properly, but I am not in that group- I do more homework than most. I had also done a huge amount of extra work organising this concert. I feel really hurt. WWYD?