Mushrooms, if not LSD. DO NOT give her 2C-I, if you're going to pick some RCs don't bother with the 2c-i/e, I certainly would've hated a side-effect ridden trip to be my first time. How about some of the other ones like 4-aco-dmt? 2c-c comes to mind as it's relatively easy and by the looks of things your mum is wanting to 'use' this rather than trip balls. I hope you've made all the effects clear to her and not merely said how some people use it for meditation, etc, it's not the same for everyone and if she's in her later years many people in this age bracket tend to find trips a lot more taxing and avoid them. Look for the lighter psychedelics out there and work her up, if it was LSD I'd be dosing less than 100ug. Carry some valium too and make sure she is aware that they are available before she trips and that they well make everything okay if it gets too much.
Edit: Just saw your planning on getting some LSA, don't give this to her either. Although plenty of people have great experiences on these sort've things, if I was personally given the choice to decide what a persons first trip was I'd try to find the easiest one out there.