Breastfeeding instinct

Sorry I know this is the wrong group but this group is the most responsive

How long do babies have the breastfeeding instinct? For a baby that was never breast fed, how long would the instinct to look for the boob be there? My baby is 7.5mo and has recently started rejecting her bottle and she seems like she’s looking for my nipple when she’s hungry. She’ll look with her mouth around my breast area (with my shirt on obviously) and if I’m wearing something with a button or something she’ll start sucking. I’m super confused where she would have gotten this (other than instinct) as she’s never been breast fed and has been a formula fed baby her whole life. Obviously if I still had breast milk I would give her breast milk if it would make her eat but I am all dried up. If anyone knows anything can they shed some light?