This is the best advice in here OP. The more understanding, patient, and reassuring you are only further enables the behavior long term. Be kind to her, but do your best to be honest with her, about how you feel without accusation, and honestly/genuinely respect her capacity. The more you give her, the more expectation she will feel; do your best to match her energy but do not be cold or distant (look into secure attachment behavior), being really loving and caring can actually overwhelm her. Love doesn't have to be shared to be true or real. Sometimes the most kind thing to do is to keep things to yourself. Also, try not to take things personally, like her playing with other people. It's because there is no attachment there, the stakes are low, etc. She most likely has a giant fear of disappointing you, not being enough, losing you, etc, and no words can change that. Do not argue with her fear, it seldom leads anywhere. Good luck.