How can one deal with recurring disagreements and constant arguments with a sister when living in the same house?

The disagreement between you necessitates avoiding friction as much as possible, and occupying yourselves with worship, seeking knowledge, and beneficial matters. Affection and love have returned between some brothers and sisters after a period of distance, so you must be patient and broad-minded until Allah facilitates marriage. No matter how long life lasts, separation is inevitable, so let it be for good. We ask Allah to inspire you both to your right conduct, mend your relations, and unite your hearts.