The funniest gym night ever

Last night my sister and I went to the gym. (Beck, please do NOT kill me for telling this story).
We had this personal training session set up where we were going to set up a routine for weights and stuff. So we had to go to the gym early.
When you have a session you have to go to the front desk and let them know you're ready.
As we were walking to the desk (maybe 5o steps from the change room) my normally reserved sister saw someone we went to school with. Specifically someone we went to elementary school with. For the sake of argument we'll call her Marsha Brady because she is just that annoying.
Neither of us liked her. She wasn't awful, just really annoying. And not someone we would choose to hang up with as we got older.
So, Becky sees her and says to me, "OH CRAP MARSHA BRADY!"
It was so loud.
Usually my sister speaks quietly. People ask her to repeat herself. Not today. I think the entire gym heard her.
So there we were, standing at the front desk giggling because she had just shouted this. And, the thing is, we're totally recognizable.
My sister has curly red hair and is really skinny. I have dark brown hair (currently highlighted) and am a little on the chubby side. When we are together, people who have not seen us in years recognize us.
I'm not sure if "Marsha" was just so focused on her workout that she didn't see us, or if she ignored us. But, she's not the type of person to ignore us, so I'm pretty sure she didn't see us.
This may have been because Becky decided to hide behind me for the rest of the evening. She insisted on finding the most distant treadmills and actually did a crouching walk to avoid all eye contact.
The highlight for me was offering on numerous occassions to invite her to belly dancing. I thought Becky may kill me.
Soon our friend left. But, I tell you, the gym is a small place. I'm sure to run into her again.
And, on another note. We had ana awesome training session. I'm totally into doing weights now. I'm hoping some of the trainer's suggestions pay off.