Playing devil’s advocate here.
As in any settled demographic, one new member with new ideas can upset the equilibirum and put noses out of joint among the old guard but presumably she was voted into the position of chair by a majority of the trustees or at the AGM depending on what the constitution demands.
After seven years, perhaps the publicity material was in need of a fresh look. It’s natural that you feel protective of what you designed but again, presumably the new look was discussed at committee and voted on.
Sadly, having stepped down from the committee, you lost you right to have a say.
Now, someone needs to keep an eye on how the new look is being received. Are flyers in the new design catching the eye of the public sufficient for them to take one when they see them and buy a ticket? That’s the main thing, that tickets are selling and your productions are well attended.
These things aren’t set in stone. I am involved with live event promotion and we design in-house. Our copy for several hundred A3 posters and A5 flyers goes to the printer once a month. Costs are low.
If the new design isn’t received well by the public, the society could always revert to the old design. It’s a choral society not a national or multinational where the slightest change of logo is extraordinarily expensive because shop fronts, vehicles, badging, labelling, letterheads etc etc all have to be changed.
Don’t cut off your nose to spite your face over this. It is just a piece of paper after all that will soon end up in the bin. It’s not unlike the thread here about revenge. Better to hold you head high and be gracious about the change, however put out you feel. The enjoyment is in the singing. I would urge you to stay with the choir.