Should I speak up and if yes what should I say about this person who uninvited us?

In my community we always get discounted tickets to go many places. I was asked if me and my family would like to go to 6 Flags this weekend for $20. I told her that I wasn't sure if me and my youngest son would go but hold on i'll let you know if my oldest son would like to go (he's old enough to go by... show more In my community we always get discounted tickets to go many places. I was asked if me and my family would like to go to 6 Flags this weekend for $20. I told her that I wasn't sure if me and my youngest son would go but hold on i'll let you know if my oldest son would like to go (he's old enough to go by himself)

On Monday, I contact her on facebook that My son would like to go. She told me there are no more seats. I just said "alright" instead of carrying on.

On Friday night, I was sitting in the court yard and a neighbor/acquaintance asked me if i'm going to 6 Flags. She said Sarah (fake name) asked her if she'd like to go and invite others because she has 11 tickets left.

I told this acquaintance that I was on told on Monday there were no more seats.

I was plenty angry about this. I know Sarah doesn't know I know what's going on but I don't want her to be fake with me saying hello etc... By the way, I checked for some picture on facebook from another who went. Her boys were sitting together but she was sitting by herself and took a picture so there were seats on the bus.

What should I say to her?
Update: Sarah had asked this other neighbor on Friday if she'd like to go. She told me on Monday there were no seats so I know she's lying.
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