IMO the fewer nap days you can do, the sooner she would settle in and get used to NND. However if she's not ready, then a nap would help to keep OT at bay. This is the first time she has had NNDs and her body needs adjusting the body clock for it. I would actually do slightly earlier bt to prevent OT, rather than fitting a nap in, e.g., on weekends, or the days that is possible, i mean 30 mins earlier, not SEBT. The restless nights are indication that she's not tired enough to get the full rest in the night.
If it is not possible to have slightly earlier bt, then slip in a nap but be prepared for a restless night which means she would again spiral down to the tired route the next day. It just keeps this transition period longer. Just my 2 cents in our situation. Is it half term with you? Is it possible to try out NNWeek? Her nights might even get longer. FX for whichever way you do. xx