Friend? or not friend?

I have this friend and were supposedly supposed to be best friends but she keeps lying to me. For example a few weeks back we were sitting in class and she turned to me and said what are you doing this weekend, so I said nothing, and she invited me to hers for a sleepover.

Later that week I had asked my mum and then texted her saying yeah I am free, what time do you want me to come? and then she text back saying oh its my neighbours birthday who's like a dad to me so I can't do it.

Yeah maybe that happened but I know for a fact she hardly knows her neighbours. and she keeps doing it. Some times I am there when she does it to another friend. She laughs about she will say oh ........ wants to come, but I told her me and my family are going out,

I don't know what to do because I know I hate it when it happens to me but I don't know what my other friend would think if I told her would she care or would she think I am trying to split the friend ship apart.

I don't know if my friend thinks it's fun, and to be honest I think I would prefer her to tell the truth than to lie. She knows everything about me but I don't know if it's worth it. When she doesn't lie, were the best of friends.

But when she does I don't know, Is she a friend, or not?