You are making an understandable interpretation from the heart as a loving mother seeing your daughter as vulnerable and so very dependent on you for things like safety, but that is the very point to be made here, that without you, she is vulnerable and on her own. You cannot be at her side every second of the day or night. You cannot know what is going on in her mind let alone the deep subconscious within her and how it might react to a spirit approaching and engaging in a dialogue and how that might shift her energies in response. This is simply beyond your ability to know and to counteract.
Every being has free will and free agency, even a fledgling human who is inadequate to the task for a period of years, in fact, to achieve a level of maturity where they can fend for themselves adequately to be out and about in the environment on their own totally. Children simply lack the experience to even know what is hazardous and what is not, let alone how to cope, let alone have the physical body, the presence of mind, the emotional maturity, and strength of conviction to marshal the needed strength and have the experience to engage with the body to carry out the desired intention. Children continue to be vulnerable for many, many years on all fronts.
So what is needed for you to be aware of is that, in the same way she is physically vulnerable, she is vulnerable to spirit attacks simply by being present. The fact she is so vulnerable does not mean the divine can step in to ensure this on her behalf. That is your job as the parent. Her mind will vary greatly largely through the emotional stimuli she generates with her feelings and this will change her intentions and her spiritual vibration, so to speak. Having a low moment emotionally is very common in life, especially in the young who take everything seriously and are easily perturbed when things are not perfect. Their feelings are extremely acute and sensitive and they will react very, very strongly to any kind of adversity. It takes maturity to learn how to be patient and tolerate even things like boredom let alone being bullied by an attacking consciousness.
Because there is an unseen realm, you will always be in the dark about many things that happen for her and this is true for you as well. This is simply the human dilemma of disconnection. You are all vulnerable, you are all potential victims, and almost certainly will have times of difficulty when your emotional vulnerability leads to being possessed by a dark energy—at least for a time. So that is what is happening with her, that her emotions are quite strong and range over a wide spectrum of extremes and during low moments she becomes vulnerable and that can be exploited and must be allowed by the divine realm.
So the answer here is to have a periodic request for safety, protection, and healing to be done over, and over, and over. It is no different than watching over her personally every day to be sure she is clothed appropriately, her hygiene is attended to, and she has nourishment to meet her bodily needs and a good steady dose of affection and love through simply paying attention to her and engaging with her and supporting her learning by participating in her life to give her feedback. You are already her greatest teacher as her mother and you are her greatest protector. You just need to recognize 100% perfection is not possible to maintain for anyone. That is part of the point of human existence, to deal with the adversity and consequences when they arise. That too will be for you to teach her about down the line when she is old enough to understand such things. In the meantime, you must do all you can to keep her going and see to her needs and happiness through making frequent requests of the divine and this will be effective to stay ahead of serious consequences.