Wouldn’t that be " in xml? i.e.
"hi "mom" lol"
**edit: ** tested; works fine:
declare @xml xml
set @xml="<transaction><item value="hi "mom" lol"
ItemId="106" ItemType="2" instanceId="215923801" dataSetId="1" /></transaction>"
select @xml.value('(//item/@value)[1]','varchar(50)')