I might have this wrong, so take this with a grain of salt.
If she continues to absorb mana, which as far as we know is the same as energy, the energy will get denser. We also know in this universe that mana had volume, hence the storage tanks seen in previous chapters.
According to E=mc^2, energy and mass are equivalent. If she continues to absorb, as we've seen from this chapter, large amounts of energy continuously inside of her, then the energy is gonna get REALLY dense.
With F = G x (m1 x m2)/r, basically saying how gravitional force, F, is given by gravtional constant G, times m1 and m2, masses, divided by r, the space between masses. To put it simply, more mass (with mass = energy) + less space = LOTS of gravity. And we all know what happens when lots of gravity is confined to one spot. Event horizon time!
TLDR - Kissing = Black hole