Mile distance on my wifes Garmin Lily is inaccurate. Seems to be shrinking.

My wife's lily watch seems to be hitting the one mile mark much earlier than my fenix 7.  My one mile mark is consistent on the route I take every time.   Hers is all over the place.  Is there a way to calibrate her lily watch?  We have tried measuring her stride and resetting the watch.  I see there have been some similar issues posted on the forum with no solution?  Is there a solution?