Your about half way there but it doesn't seem to be hitting you it's landed one hit that was then deflected by shield. In my eyes it's becoming a slog.
Asha pulls a diamond from her pouch. She cups it in both hands and speaks the words of power. As she spreads her hands apart the diamond begins to float between them pulsing with green light. As she finishes her spell a sphere of green energy streaks towards the plant thing. The green sphere burst as it strikes the creature splashing acid across it's bulk.
The party once again strike out at the writhing mass of foliage, bone and hide in front of them as blade, spell and arrow all stroke the beast in unison it is difficult to judge the condition of the creature but you get the feeling it is coming to its last legs.
In return the creature once again tries to engulf Ana as it pounds her twice knocking the woman to the ground and then everything goes black and Ana can't breath she appears to be trapped inside the mound the moist decaying leaves and flesh press down upon the woman's chest making it impossible to breath or move. From the outside Ana's arm can be seen sticking out from the mound slowly being dragged within the mass.
GM:
Ana suffers 6 then 11 points of damage from the slams and its now inside the mound blinded, restrained and unable to breathe and must make a dc 14 con save at the start of the mounds turn or suffer more damage, other than that the engulf is just a fancy grapple and can be broken in the same ways. Ana also loses a vitality point.