ATCOs in TXL do both tower and ground duties, and at times even clearance delivery although that is usually done by a flight data worker. So you can have encountered her, and other, on both frequencies. I believe that is quite common for DFS run german tower/ground frequencies. Only apron, if it does exist, is run by a different unit. TXL doesn't have an apron frequency or unit. Since there is basically only one taxiway everything that is done on the "apron" as it is, has an effect on the rest of the airport.