Me and my Sis have worked out various schemes over the years. We still like to give each other birthday and Christmas presents but neither of us wants to be landed with a selection of unwanted objects.
Our solution is food and booze. Hampers, actual food, or vouchers. We also send flowers or plants. We don't live near each other so we order online and have the stuff sent to each other.
With regard to the unwanted experience, I am not sure what to advise, given that I don't know what it is. If it is something like sky-diving or bungee jumping then you are quite justified in saying you just can't but thanks for the kind thought. If, on the other hand, it is just going to be a bit tedious like folding towels into animal shapes, (apologies to anyone who would not find this tedious. Each to their own) then I would just go and do it and remind yourself than nothing goes on for ever.
Are you sure you still need this woman's friendship? She sounds rather overbearing and doesn't seem to have tried to get to know you very well.