Trying to open Premiere Pro CC 2017 on a computer that has Premiere Pro CC 2018

My boss and I have two separate computers right now. I have a Mac OS X Yosemite 10.10.5 and she has a Mac OS High Sierra 10.13.6. I work from Premiere Pro CC 2017 and she works from Premiere Pro CC 2018. As of now, she can open up projects that I have worked on, but she has to save it as her own project to work from them. If i try to open up the project file she created on her computer on mine, i can't. She can open my versions, i can't open her versions on my computer. A quick solution would be to buy another computer but my computer is not that old. We have tried sharing XML files back and forth, which for the most part work but not all the time. Recently she exported a sequence in premiere from her computer and when i imported it on my computer, the sequence was there but audio didn't match and clips weren't correct. Whats the best way around this. We both are usually in the office, so its not convenient for me to go on her computer all the time to work on a project that she started on hers.  Her Premiere Pro is 12.1.2 and mine is 11.1.2. How can we share projects without this interference.