The support of our trio is dead, and even if they didn't, assuming that the trio would never have to split up would be a bad assumption. Ebony as far as we are aware, has no healing spell, and neither do we.
It is fine to be a dps focused magical girl, but over specialization is just as dangerous as generalization.
Having a way to heal others in an emergency isn't bad.
I say though, rather that I am not really sure of using "regeneration" as the base for the healing ability, if only because it is slow when used on us until it gets to a much higher level, much too slow to be combat viable. Using it on someone else will either have their own internal magic make it utterly fail at first, or be just as slow, if not slower than when used on us at low levels, and while a healing spell is good, going that specific route seems like something that would take a lot more focus to have it be usable in combat to heal someone, or to save someone on the verge of death. Though, conversely having a percentage based heal to use on others would be really beneficial if we got it high enough to matter when we need it the most, but that would also be taking a lot of time from other things to make it that viable.
Plus, I imagine the way regeneration works (Works by directly feeding cells magic instead of the body's energy.) is more unattributed than it is something with the "beginning" or "end" affinity.
I could be wrong though if it considers Regeneration-->Life-->Beginning which but I am still uncertain that is the way to go.
In fact I kind of like Shadow's Warm aura of healing more Heat-->Beginning, Healing-->Life-->Beginning, so it definitely at least has as strong or stronger a connection to Beginning. We aren't near good enough at control to use healing fire but healing warmth is probably less dangerous.
Though of course there is the argument that it might just be better to wait until we are better at control and just go the healing flame route once we are there, though that too runs into the risk of then not having something when we really needed it.
Spending some time on healing is more likely to save lives than it is to screw us over.
This is a quest that plans to take a decade or more in game, spending some time actually getting viable healing is probably not going to be a game ender, and more likely to be something that prevents an unnecessary bad end.
edit: That said it isn't like I don't see the appeal of flight, since it is both useful and something that Cerys explicitly liked doing when she first managed it, but if I were to use flight as a method of calming down or getting her to feel better I wouldn't put it as do something productive with your time or practice flight.
I mean, the Light will dim eventually.
