A really hard situation , but if Mum doesn't want to go , then let her be.Travelling , staying overnight and so on can be taxing at any age ,but even more so if you are elderly.At Mums age a funeral is perhaps even more upsetting than for a younger person , she may be all too aware that her own mortality could end sooner rather than later.She may have some real anxieties about this and a funeral would re-inforce these especially as you have had a number of these to contend with.
Is it possible for you to go , and represent Mum , having arranged for her to be kept an eye on whilst you are away.
Think the wishes of your mum are paramount in this issue , she should not be pressured into doing something she doesn't want to do .Hope things work out for you all.