Spotify Volume Control with RooPieee XL

I just got a Rasberry Pi 4 and set it up in a case with Roon PieeeXL running to my Schiit Modi DAC and then to a Rega Brio. For Roon I love this set up! I may eventually invest in a HAT but for now it sounds notably better than Roon over my Audio Engine B1. My partner has a Spotify account and prefers that, so I set up the login in Spotify for her and it works just fine and I believe sounds a bit better than the bluetooth. It’s a small annoyance but she would like to be able to control the volume ideally with the volume buttons on her iphone, but even with the Spotify volume slider that would be fine. At the moment she seems unable to do this. I have the settings under LibreSpot in the RoPieeeXL settings set to Volume Control: Software. If anyone has any idea on how to make this work it would be greatly appreciated. I recognize this is not technically a Roon feature but this seems the best place to ask and maintain harmony between platforms!

I’m not familiar with some of your setup, etc., but would it solve the problem if you put together another RPi4 just for her to use with Spotify? If necessary, WIFI seems to work well with the RPi4. An RPi4 in a FLIRC case running RoPieeeXL is only $75.

that may be what I have to do, but I was really enjoying having it all set up in one box, also, I’d have to change the devices feeding into the DAC since it only has one USB input every time I switch.

Maybe a USB splitter would work.