I’d say be patient. She could be used to being the center of your attention and it’s hard to share you. Often times kids that age dont know how to identify jealous feelings so they say things like the other kid is too young, or the house is dirty. Have the next few visits be ones where the moms and kids are engaged in fun activities together (art or crafts project, outdoor game, etc) so she can experience you and the others at the same time, then once you see them engaging with each other and starting to form a relationship you’re on the right track.