22 dating 27 is not a big difference at all. My mom was 20 when she met my dad, who was 27. Many couples I know have an age difference like that.

Now, when it comes to an age difference where one partner could potentially be the parent of the younger... while, things do change and it's easier to mix up signals.

Using the barista - she may very well be extra friendly and chatty with men significantly older simply because she views them as "safe". She might be more brief with men around her own age because she's more conscious of not wanting to lead them on. She might miss the older man's attempts at flirting because she isn't expecting them, where with younger men she will be more alert and is thus more ready to either reciprocate or reject openly. With the older man, she may try to be much more subtle just in case she's imagining things.

I say that because that is my own behaviour.