@mack505 The only ones I really hear of are OnlyOffice and WPS Office, but I’m not sure how those particularly function, since the former is said to just be a web app wrapped up like a desktop application.
There’s also FreeOffice, but Softmaker is behind that and really wants you to subscribe.
The real question though is what variation of MS Office is she using or has used the most? If it is 2003/2004 or earlier, then Libre/OpenOffice dislike makes very little sense to me.