My theory is that the Helena we see in Servants of God is actually the daughter of the one in the second game. If it had been about 50 years since the end of TRPG2, it wouldn't be unlikely for her to have a daughter in her late forties in this game, and for the daughter to bear the same name as that of her mother and her prized mercenary group. (I have not yet interacted with Helena in length, however, so I don't know if she later presents any contradicting information.)
Contradicting information is later presented, according to the wiki. (Open the spoiler for details...)
[spoiler]
If you capture Hellion for Festus, he arranges for Helena to give you a discount on troops, as a friendly favor. Which means that that
is the Helena he knew personally, from TRPG2.
[/spoiler]
So yes, that's not her daughter, that's actually her.
By the way, this is a bit of a tangent, but do you think it's possible for psychics to extend their lifespans? Many fantasy stories talk about ancient wizards preserving their life through magic, and though the Gift is a bit more grounded than most fantasy magic, I wonder if a similar thing is possible. We know that Nelis, at least, was thought to be immortal, implying she outlived even the long life of a shadowling, though it's anyone's guess how she actually did this.
Even if it is possible, though, it doesn't seem like the characters we know used it; the Nameless One and Anya both appear to have aged naturally.