The girls who do our mobile services would charge £10 per 30 mins rather than a flat fee as you never know what you are going to find when you get there! And then 35p per mile for travel.
It is good that you have empathy for her, which shows you care about your clients, but if we are running a business you shouldnt be doing it for next to nothing just because she doesnt get on with them.
As you know hair extensions aren't for everyone given the work required to keep them looking good, but this is not a basis to give your time for nothing.
Thats just our opinion and the way we work ourselves.