I was flying on an Emb 175 - 2 FAs - sitting in 4A - the last row of FC.
1 FA was making the drinks after takeoff, the other was doing snack try duty.

At the beginning of the service, I noticed the FA take a banana from the tray and put it in her sweater pocket with half of it sticking out. When the tray got to me, there were no more bananas left so I asked if there were any more up front. She told me no they were all out, the banana she had took was right in front of me, I glance down at it and back to her and said all I really want is a banana. She said sorry, we're all out. She then walks back up front, sticks her hand in the pocket and jams the banana down so it can no longer be seen.

After they had completed drink service in coach, the first FA who was handling FC comes back down the aisle. I told her what happened and she was very apologetic and said that customers should always have first shot at what's in the basket and that I should write DL and they would do something about it. I told her I didn't want to make a big deal out of it - I just thought it was bad form and that she should know about it. She reiterated that I should write DL.
This is when I started to think that there might have been other issues with the second FA as the first one was pushing me to write a letter.
Is this really worth a letter?