Girlfriend has higher score despite us only having each other added

hey my gf has a score that is 9 higher than my own, we only have each other added and its been that way the whole time as they are new accounts. the score has incrementally gone up by 1 or 2 more than my total score over the past few weeks. she showed me her snap and only im on it and the downloaded the data and there wasnt anything there although i didnt personally see her download it and just saw it in her files after it was already downloaded. is there anything that can explain the score discrepancy?