I'm not a drop person. POTC is at the very threshold of what I can tolerate without getting sick for the rest of the day. I wouldn't downplay the drops. I would be very honest with her and try to help her with strategies to make it more tolerable for her to try.
If she decides it's not for her I would not shame or guilt her (not that I think you would) in any way. I can't speak for everyone, but I avoid drops because they cause me serious physical pain that can last for days afterwards.
ETA - I looked up the drops, both are at 21 degrees, the first is 52' long (not high) and the second is 37'. I don't know if that sort of info helps your mom...