what does "slash"here mean？
She put her hands to her head, did a little dance in place. “Dinner date. I have to wear heels to make it look real. Okay, okay, I’ll stuff some sneakers in my bag, change shoes for the jog back. And don’t give me that look. Footwear’s important.”
“We need to talk it all through again, and I need to fill you in on how Sherrilyn’s playing into it.”
“Then let’s do it downstairs. I need to put away what I got at the market before my encounter. Then I need to figure out what to wear for our fake romantic evening-slash-ambush.”

Question

what does "slash"here mean？
She put her hands to her head, did a little dance in place. “Dinner date. I have to wear heels to make it look real. Okay, okay, I’ll stuff some sneakers in my bag, change shoes for the jog back. And don’t give me that look. Footwear’s important.” 
“We need to talk it all through again, and I need to fill you in on how Sherrilyn’s playing into it.” 
“Then let’s do it downstairs. I need to put away what I got at the market before my encounter. Then I need to figure out what to wear for our fake romantic evening-slash-ambush.”

Answer

I'm guessing, but I may be right.
I believe the word 'slash' represents the punctuation mark ' / '.
The slash is used to take the place of 'and/or'.
The slash I've written above is called a 'forward slash', like a person falling forward, i.e., falling head first.
The other slash is called the 'backward slash', like a person falling backwards.

And that's my best guess...

Answer

It's part dinner date, part ambush. A cross between the two.

We also have 'dinner-cum-ambush.'

It bit of both.

Answer

It 100% means the punctuation mark "/" - in the UK you would quite often write or verbalise the word "slash" to indicate that you want to describe a fusion of two things.

For example: "The restaurant was sort of Indian slash Mexican - very strange", or "I am hungry slash tired". It is a very modern, internet-age thing.

In your example, I assume that she is preparing to go out for a pretend/fake romantic evening which is actually an ambush of some kind.

I hope that this is helpful slash useful.

Tom