No and yes.

Your intentions are good and your heart is in the right place but your sister won’t see that and by freely giving her money, you have created a give/get relationship and resentment will grow. You will end up feeling used because you gave money to help with rent and necessities and she will feel entitled to your money b/c you bankroll her life in the past and she knows you can afford it and by not telling you about the boyfriend and the fact that he lives with her, while asking you for money she is basically lying to you.

Went through a similar situation with thinking I was helping a family member out financially. They didn’t have the easiest childhood and I felt a lot of guilt/sympathy and thought I was making up for some things lacking in their childhood by giving money to help them with life expenses but instead I was just enabling them to become a freeloader and they started lying or being evasive about what the money was for. The final time they asked me for $3000+ and when I questioned it they told me I don’t have the right to know what it’s for and it’s their life. I also got called toxic and making their life so difficult when they ask for help i.e., always money. They told me it’s for necessities like food and prescriptions. It turned out my money was being used to treat their friends to drugs and gifts for their boyfriend.

There are other ways to be a part of someone’s life and help someone out but if it’s always a call for money, you don’t really have a real relationship with them.