Well, time to over-analyze everything Muma said.
There is the "terrible icky gross monster". While that is not much to go on do pay attention to slime trails and bad smells. If you do notice a sudden bad smell your first reaction should be to draw your dagger and get ready to blast the monster with an Icicle, not to check out what smells so bad.
It might just be a flower after all, but looking a bit silly waving a dagger at a flower is preferable over you getting surprise-attacked by the monster. And maybe there is another fairy on the floor that's prettier than Muma and she is over-compensating with her description.
Do be weary of "sunshine, happiness and pretty plants". The tower isn't just nice like that and you haven't earned it as a reward yet, so it may be a poppy field that puts you to sleep with happy dreams until you die.
There doesn't seem to be anything we can do with the knowledge that there are ways to keep Muma or to leave her behind, but we should remember that when choices appear. For now though we should favor the one that doesn't get her killed.
Try to properly understand the lantern logic. It's important to know if areas are considered "connected". Apparently this is something that Muma is allowed to talk about, so ask her to tell you when you're leaving an area. If that is not allowed then ask her directly whenever things start looking differently than before.
Since the tower seems to like rules so much try to find ways to abuse them. The monster is probably not allowed to go into the safe lantern area, but you have range and can blast it from the lantern area or can retreat to it, forcing the monster to turn around or get punished. Maybe you can remove the lanterns to make it look like it's not the lantern area, but it still is, thus the tower kills the monster for you.
Try to find a way around Muma not being allowed to tell you things directly. See if she can draw pictures in the dirt instead. Maybe she is not allowed to bring things up herself but when asked a specific question she can answer. So try question like "Would I be able to defeat the monster?", "What is the next danger I'll encounter on this path?" or "If you had to make this choice which option would you pick?"
Lastly, Muma doesn't seem to have much trust in us and seems to prefer we weren't here or you wouldn't listen to us. I don't know what to do with that information yet. We are an integral part of the tower, she should know that. It might be something innocent like the loudness or that she doesn't trust us to suggest the choice she wants you to make, but it might be more sinister.