Good point here. Vaping is generally not meant to be "mouth to lung" the way a cigarette is. Even equipment that states that it is meant to be used MTL is generally going to be much smoother with a direct lung pull. Tell her to try inhaling deeply, from the vaporizer all the way into the lung, instead of pulling from the device to the mouth, then into the lung. Not sure how the FUMA works, but it may help smooth things out.
One last thing, nicotine content is everything. Salt nicotine juices used in a lot of these newer pods can run from 25-50mg. That is a ton of nicotine. The average American cigarette contains just over 9mg, of which only about 8mg converts to free nicotine in the bloodstream.
More nicotine makes juices much harder on the throat. I have been vaping for about 10 years, smoked since I was 12, and I can't do salt nic, it is too harsh for me. Personally, I like 3mg for a smooth hit. But I use 9mg most of the day right now to be comparable in nicotine content to a cigarette.