Tough, but you need to look at this objectively. When she says she feels that you don't love her because you never play with her tell her, "Oh, but I do love you" and remind her of the last few times you played together. Be consistent whenever she says this and don't allow her to manipulate you through guilt or confuse in her mind what is truly going on.
This may be more of a want than a need of hers, she has to accept the reality that she has to share you with her sibling and you have things you need to do. But if indeed this is her love language she will need to find a way to nurture it along on her own, by helping you when you need help, by doing things with you that you need to get done, or playing on her own contently by your side in order to be with you. Because realistically, who in her life is ever going to always be with her, every moment she wants them there, to do what she wants at that moment?
Show her your love with hugs and kisses, call her attention to the times you play together, "OK, let's play such and such!" remind her of the times you've played, and she will see it.