In our case BM had left SD with her grandparents and took off to live with an internet boyfriend. When BM was told by the court that she either come back or loose custody, she came back. BM was doing a lot of bad mouthing and talking to SD about how bad we were for doing this to "them".
It was during this time after BM came back before the court stuff stopped that SD started frequent bathrooming. She also start washing her hands until they were chapped and cracked.
SD was in counseling then. The counselor at the time was very concerned about her "OCD" behaviors and her body image issues and was concerned that at 5 she was developing an eating disorder.
Our SD had a lot more going on. So I can't tell you if she was doing the frequent bathrooming because she was 5 or because of everthing else.
The frequent bathrooming stopped after about 6 months. She didn't stay in counseling all that long. She didn't end up with an eating disorder and I don't see any of those OCD behaviors anymore.
Maybe give it a couple months and see if it's just a stage that some 5 year olds go through.