She still has five months of learning, maturing and developing to go before she starts. That’s a lot of time to gently work on her confidence, self esteem, social skills and personal care skills. Remember while it might not sound like a lot of time to you it represents a lot of time in terms of her overall life experience.
Dressing and undressing will soon become much easier as the weather warms up, if you can encourage her with easy to put on clothes like t shirts, pull on shorts etc she will start to develop skills to deal with more complicated clothes come the autumn. You can also help her to improve her hand co ordination skills and muscle strength using things like play dough , threading beads, sand castle making, duplo, jigsaws etc.
Learning to do up buttons and zips is a skill, sometimes easier to learn on toys or other objects than clothes. Put markers on her shoes so she can put them in the right orientation as a first step to putting them on independently. Encourage her to take responsibility for hanging her own coat up ( on a low hook) putting her shoes tidily and her dirty clothes in a washing basket, tidying up her toys and books, picking her pjs off the floor, clearing her own plate and cutlery from the table. Lots of praise and encouragement for being a clever big girl. Extend the responsibility to doing things like putting table mats out, finding the salt and pepper shakers, giving the cat his biscuits etc and other little jobs that she can perform independently .
Walk past her school if you can, and talk about what you see very positively, it’s all a bit different as there might not be many opportunities for settling in sessions. Might be worth contacting the school when they go back to see if it is possible for you to visit. If it is, take lots of photos of the school so you can talk about the classrooms, the hall, dining hall, the toilets, the office so it becomes familiar.
If the toileting hasn’t improved naturally ( which it could well do) then make an appointment with the Senco at the school to discuss it , maybe ask for a meeting with someone from the school nurse attached to the school.
I am sure she will be fine, reception teachers are used to having a wide spectrum of children in the class, from the super confident to the super shy. Try not to let her sense your anxiety about her, we often take cues about our expected behaviour from others.