First, I would say, yes mystics and healers, like anyone really, do get attacked.
But there is more then one way of attack, and there are a lot of differences in origin and intent so I would be reluctant to point it out as demonic by default, as it could have a lot of other 'roots'.
People that are sensitive, are 'easy' targets. I suppose it is a bit of a 'high payload, minimal effort' kind of thing for whoever is doing the attacking. Mystics and healers leave a part of their energy somewhat open to this as they need to use it to heal. In this way they will also come across residual energy, that they unintentionally picked up and did not cleanse.
A lot of this residual energy in the same person can build up and even feel as an attack, when the bucket gets too full.
Then there is the other sensitive, people that are sensitive in character, who are in that way also easy targets because words can easily bring them off balance, which is a state that is beneficial to any attacker.
That being said, I have not encountered anyone still being attacked after their death, not energetically that is. Not saying it does not happen, just, that I have never heard/seen it.
Now, I see two things here, possibilities.
The first being, children are usually unfiltered and direct in their responses. So what you perceive as malignant and attacking, could just be a not so diplomatic response from a child.
'She left already' in an annoyed manner, can just as well mean that they are sad to not have her around anymore but, they do not yet have enough experience to say this in a way that does not offend others.
Just putting that out there to give you another perspective.
The other option is that you yourself have too much residual energy you have picked up along the way, and it's simply too much, like I said, this can also give a person a feeling of being attacked.
There used to be a great post on here about taking back energetic chords that are connected to others, by sshenry, however I cannot find it at the moment, and I need to be out the door soon.
But I would recommend you clean your own energy that way, to see if you still encounter the same things after. Just a simple process of eliminating possibilities and cleaning your own energy is an easy one.
If you are interested in that, I can see if I can find that thread when I come home from work, or post the basics myself here. Let me know.
I hope this helped.