She is undergoing a LOT of stress & anxiety.... remember, a young child cannot cope with all of these things...they cannot carry the whole world on their shoulders. It is an enormous burden for them.
Whenever children has stress or trauma... they regress. Bed wetting every night, is a regression. This is a "signal" that something is definitely wrong.
It seems you are very worried about her, and rightly so.
But, please don't just ignore it or let it go on, and on, and on, and on, and on.... hoping it will just go away or she will "outgrow it."
There comes a point, when, a child needs EXTRA help in coping/adjustment and direction, when they have problems. So, if Parental help does "not" help them... then you should seek out alternative help... appropriate child counseling etc.
When a child is "scared/worried"... they are not just "scared" as an adult would be... because their level of maturity just does not understand fully... and everything is super magnified and ENORMOUSLY "more" and their imagination gets them angst ridden and they don't have the rationality of an adult.
When my daughter started preschool when she was about 4 years old... this was also the time I had my 2nd baby... and on some occasions she started having pee-accidents again in school and at home, and in bed. It was just so much for her to adjust to... school and her new baby brother, and her just developing all kinds of emotions. Anyway, so we talked with her all the time, we spoke to her Teacher (and yes, they are quite keen on understanding adjustment issues for the children), we never pressured her or "scolded" her or embarrassed her about it... we spent extra time with her, we did all kinds of things to help her feel closure and in balance again. And, it helped, her pee accidents went away and did not last long.
Kids DO get stress and anxiety and problems emotionally... it will either impact them for a long time... or they will adjust... their "resilience" ability varies according to the child. No matter what... they have their own time-line in how they "heal" or get back into normalcy. So, the Parent must "let them" be and support them no matter how long it takes them. Kids are tender...
Maybe ask your Pediatrician about positive ways you can "help" her... sometimes role playing helps. I would also speak to her Teacher about it....so they have the head's up. Tell them what you have posted here. When it comes to our children, we can never be too "shy" or reticent in helping our kids... and speaking to the Teacher if need be.
Take care, I'm sure your girl will be fine.... but observe her and gauge her, monitor her and do what is best. Everything in her life is a big deal now. What a full plate she has.
All the best,
Susan