multipoo puppy need advice asap bonding issuses

we have a MAJOR problem. for our daughts 8th birthday we just got her a multipoo puppy. she is very nice to him and they cuddle when he is sleepy but other then that he wants nothing to do with her unless she is feeding him or has treats... He flat out INGORES everyone but me (mother) evan my husband. I dont know what to do.... We have her give him lots of treats and she feeds him and when shes not in school he takes him out to go potty with me ( i go because i just dont want her cleaning up dog poop and we have a small area we take him to do that) I dont know how else to help them bond if he cant bond with her i dont think we will be able to keep him and we dont want to get rid of him but idk what to do if its a puppy thing that he might grow out of? Its furstratin the pet shop we got him at instisted that they bond with all there family members but he doesnt want anything to do with anyone but me PLEASE any advice would be so helpfull thanks for taking the time to read my thread