Trainers » Mallow & Lana | Attacks » Moongeist Beam
If a Pokemon was attacked with Lunala GX's "Moongeist Beam", does that block Mallow & Lana from healing it?
The first part of Mallow & Lana says to switch your Active Pokemon with one of your Benched Pokemon. When your Pokemon is switched the effect of Moongeist Beam is removed, so then you can heal the Pokemon once it is on the Bench.
Source: TPCi Rules Team (2020-02-27)
Trainers » Mallow & Lana
You can play Mallow & Lana as long as you have a Benched Pokemon. But if your Active Pokemon is not damaged, you cannot discard 2 cards from your hand.
Source: Cosmic Eclipse FAQ (2019-10-18), TPCi Rules Team (2019-10-31)