She does care for you! And if you're the primary caregiver and parent, she likely simple trusts you'll always be there for her. She may think of you as her port of safety. Sometime toddlers (and adults!) take this for granted. Toddlers are still developing attachments and ways of communicating dynamically at this age. Separation anxiety can re-occur and emotional responses to bonding are changing as she learns to walk and talk at age one. One day toddlers will cling and reach for one parent, and the next they can change their preferences. They are finicky at this age; it's normal!
Do your best to trust your love from your child. Try not to react or show her disappointment when she runs to see her father or Grandma. She'll pick up on that. Often children respond to reinforcement or reactions they inspire (even when negative) from their behaviors and it encourages more of it. Support her, involve her in your life, and keep your routines stable so she knows what to expect. Like many phases during toddlerhood, this frustration will likely change within weeks.
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