I will second the suggestion that a **sudden** onset of anxiety and needing to confess, especially in someone as young as her, sounds like PANS/PANDAS. The most common age for this to start is 4-8, so she's right in the middle of that. PANS is a post-infectious auto-immune brain inflammation. The PANDAS subtype of PANS is the result of a strep infection that wasn't even serious enough for you to catch as strep; perhaps just a sore throat. Antibiotics, anti-inflammatory medications are the best treatments, and the earlier started the faster this goes away.
If you were half-way through a rotation, rather than just gone, that doesn't sound like you were the trigger for this intense anxiety.
In PANS/PANDAS, sudden onset of irrational anxiety, esp. separation anxiety, OCD, (including needing to confess), anorexia, and frequent urination (even new bedwetting), and behavior regression are common symptoms. The cause is an antibody attack on the brain, not anything anyone did - not her, not you, not classmates or anyone. If it is this, then anti-anxiety meds, prayer, meditation, sleep, won't take care of it; needs medical treatment for whatever underlying infection. ANd if that doesn't do it, then yes, follow the info on Pandasnetwork.org or Pandas Physicians Network (ppn.org)
Also - do you feel guilty that you aren't home? You are asking if she might feel guilty. Well, it can rub off. You both need to talk to each other. Openly. Don't go the diagnosis route, the therapist route - I mean, that's extreme. She sounds anxious. Are you? Mediation is excellent. Are you present? When you are there, is your mind there? In the moment? Or are you somewhere else? Is she trying to get your attention? Do you give her praise? Genuine praise and respect? It's all crucial to the health of a human being. Any of us. 6 is an important developmental age. You must learn how to do this and not pass it off to a therapist. Get a therapist for yourself.
Also - you just said something very important: you said that you are wondering if that is why she feels the way she does - you being on tour. Have you asked her? Ask her! Open communication and expressing feelings are very important life skills to have. You must do this. Don't ask us. Ask her. Show her you value her intelligence and the ability to work through a problem.
Definitely don't tell her what she needs to do. You don't even know why she is doing what she is doing. Seek understanding first. Always. Ask questions. Don't dictate or invalidate. She isn't telling you for your benefit. And she doesn't need you to tell her to just let it go. That doesn't help. That's not teaching, that's telling. That's ordering. A 6 year old doesn't know how to do that. Get on her level. And if you can't, learn some childhood psychology. Read books.
Also - what is your parenting style like? She seems very insecure. Are you doing things to build her confidence? Are you letting her explore her environment? Or does she live in a shaming and controlling environment? This is where parenting comes in. You have to be good at this part. This is the part.
Ask her questions. Ask her about her feelings. Just listen. SHOW EMPATHY. The child is only wanting someone to share with. If and until you relate and actually respond in a way that is friendly and supportive, then they will just keep going. If they do, then it is okay to ask them why they want to tell you everything. Ask them if they don't feel like they are getting enough time. Ask them if they feel anxious. TEACH THEM coping skills. Is she anxious? Teach her meditation. Breathing techniques. Distraction techniques. You do not want to set her up for failure by relying on external validation or reassurance or whatever it is she is doing. So, #1 ask her and listen #2 teach her how to handle it.
Don't just nod your head or tell her how she should feel or tell her what to do. That's not your job. Your job is to empower and teach.