It depends on the Bernina machine and how you are going to use the design. If you have a computer connected to the Bernina and "Read" the design to the machine, you need the file to be in the ART format. However many of the new machines have a USB port on the machine. (Bernina 600, 700 and 800 series have a USB port. I'm not sure about the 500 series that embroiders, but I think it also has a USB port.) If you are going to put the design on a USB stick and put the USB stick into the machine, you have to use the EXP format.
However, you have the Bernina software, you can open many different formats. I have opened PES, HUS, JEF, EXP and changed to ART and EXP formats. To do this, "open" the file. If you can't see the file, make sure you tell it to "Show all files". The default is to only show ART files. After the design comes up on the screen, tell it to "save as". Then you will have a choice is to the file format you want to save it as. Choose ART if you are going to have the computer connected to the embroidery machine or as EXP if you are going to be using a USB stick. I do not know what format Embird uses but I have been able to open Babylock files and change them to EXP files to be used on a Bernina 635. So if she can save as EXP and you are going to be using a USB stick in your Bernina, you can make it work.