Their relationship started because he kissed her and called her "his girlfriend", a day later his father died and she's still with him after 1 1/2 years because she just couldn't get it over her heart to finish the relationship and she had no other boys to care about so she just suck with it. but now cheated on him with me.  
i'm trying to convince her that it isn't her fault that his dad died and that she has to end the relationship with him because it's better that she's saying the truth then lying to him. 

in my opinion she's not looking out for herself on cost of her mental health and i'm really worried about her... on other side i admit that i am really jealous for not beeing the partner that she shares with everybody...

&amp;#x200B;

(english isn't my native language i'm sorry)