What should i do about this facebook problem?

oneday a girl named donna added me on facebook. she wrote on my wall the next day. she told me that she knew someone i am friends with called tara. she told me that she used to play with tara in primary school and a bunch of things tara used to do as a little kid. i wrote back on donna`s wall, saying i didn`t have the slightest idea who she is. i don`t know her and cannot understand why she is telling me about her friendship with tara. i don`t care how she met tara and her little sister, jemima, or how well friends she used to be with them. it is none of my concern. then she wrote on my wall again, telling me more stuff my friend tara used to do as a little kid, such as making fart noises with her armpit and acting like a monkey. she wrote comments on my photos too. she even asked me questions about me like which nationally i am, what it was like at my school and the area i live in, what subjects i am currantly studying and the grades i get for them. why would donna do that? she is a strange girl. what should i do about her?