How do I deal with this woman?

She is being nasty to me and saying that I don't volunteer enough of my time to a fundraising organization that I am a member of. She is the president of the organization. I put a lot of time into helping with the secretarial end of things, but she is mad because I won't help with making phone calls to help find workers for fundraisers, and I can't help at the fundraisers. I've told her that I can't help with the phone calls because I live in another town and the calls are long distance for me, and I haven't been able to work at the fundraisers because I have a full time job PLUS help my husband run his business. I can't afford to take time off work to do volunteer work. My husband suggested that I just quit the organization altogether since it's causing stress and I get nothing out of it. I don't want to quit because I don't know who would take over the duties that I currently do, and I do enjoy helping in the ways that I can. She is treating other members the same way.