5 year old 'forgetting' how..

to write her numbers and letters? She goes to preschool Monday-Friday from 9:30-1:30 and we work with her at home at least every other day as well. A few months ago she was able to write the entire alphabet correctly and write to 10, sometimes closer to 20. She now writes at least ten letters backwards and can't even write to 5 correctly. She does a backwards 2, 3, 4, and sometimes 5 even. When we ask her to write her numbers to 10 she does those listed above backwards along with 6, 7, and can't remember how to write 9 at all. This has never been an issue before. Her teachers brought it up at conferences as well... they asked if there's anything we want her to work on before she goes to Kindergarten this upcoming school year and I mentioned the backward letter making and they said "we noticed that recently too." ... what's going on and how do we help her? No matter how many times we try to practice, she still does it? It's frustrating for her as well as us when we KNOW she knows what she's doing, or used to anyway...  

Has anything changed in her life recently? Even a little bit of stress could cause a 'regression.'
Heathen is 4 and does pretty good with her letters and some numbers, but her dad is deployed right now. Whenever she gets really sad and starts missing him again, she starts to do stuff like that (reversing letters and numbers). And she gives up on reading for a few days.
Only thing I can say to do, is not make a big deal out of it. Continue to work with her on it, just don't let her know that its getting to you too. Kids can pick up on things from you as well.

My 4 year old does the same. He can write certain words perfectly fine one week then he starts writing letters and numbers backwards even though he knows the correct way. I figured it was just a learning process or something.

My 5 yr old is doing that. So far we have been told its because of his ADHD and anxiety.

My four year old is like that but he's autistic.

He knew nine letters on testing day and the teacher did it again the very next day to try to up his score and he knew zero. He does that in every aspect of life though.

Her egg donor came back into her life thanks to a court order. Her 'mom' hasn't been in her life for 3.5 years. She will be 5 in 16 days and since the court order happened a year ago (her mom is allowed to see her once every other Saturday) she still hasn't been consistent in doing so and just leaves her with her mom, Lo's grandma and goes to get high and wasted. So I'm assuming that is the stress causing all of this,but then again I'm not sure since the court order started a year ago and this behavior is just starting a couple months ago. She's pretty oblivious to the entire situation because she doesn't even remember her bio mother. I've been raising her since infancy so she just thinks she's going to grandma's house to play (we've let the grandma have contact) almost always.

That is the only thing I can think of that has been causing stress. She's been having a terrible time listening too and she can't sit still very long at all so it's hard to work with her a lot of the time.