- Maybe this is nothing and she was just confused as to which night it would be most fun and relaxing to go for dinner and drinks. Maybe she felt rushed trying to get out of work and to her class.
- Maybe OM was originally not available but suddenly found time in his schedule.
- Maybe W was trying to resist the temptation to see OM and to try to see if we could have fun together instead and she waivered.
My vote, FWIW.
You're in a real entrenched react mode, here. Think about what she said (or you think is probably going to say) before responding. Or have a couple of stock-lines at the ready to buy you some thinking, deciding time:"Listen you caught me right in the middle of something; I'll call you back in 5 minutes." or simply, "Well, that's a bit of a twist. Let me think about that and I'll get back to you when I decide."
$.02
Gardener
"My soul, be satisfied with flowers, With fruit, with weeds even; but gather them In the one garden you may call your own." Cyrano deBergerac