My sister is making life difficult and affecting my chance to marry - need advice

Salam aleykom, dear brothers and sisters. I’m in a tough spot and would appreciate sincere advice. I have one sister - our parents passed away when we were young. She’s married and lives abroad, but also keeps an apartment here and wants to store her things at my place. When I ask her to remove her belongings she threatens and pressures me, and then involves our extended family in conflicts so I look like the bad brother for “not taking care” of her. When our parents’ assets were divided, she took our mother’s apartment and some jewelry, and I received our father’s house - that was the agreement between us. The bigger problem is that whenever I start talking about marriage or let a woman into my life, she stirs up fitna and betrays my trust in ways that damage my relationship with the woman. I’ve done a lot for her in the past - I’ve travelled abroad to pick her up and supported her - but now those sacrifices are making my life difficult and harming my chances to build a household of my own. As I understand Islam, once a sister is married she is primarily the responsibility of her husband; she’s no longer under a brother’s guardianship in the same way. Am I correct? What are my rights and obligations toward her at this point? Am I being unreasonable for wanting boundaries so I can marry and live peacefully? Jumua Mubaraka and thank you for any guidance and dua.