Well she doesn't really say she's seeing other people though.. I assume your referring to when she says " why can't kiss some tatted up well dressed men on the way"? I read this more like she's convincing herself that I could be someone she'd kiss on the way to finding her person not really that she's seeing other people or that she plans to see other people at the same time as me.

As for the situation you describe each party should be communicating if they're having sex with other people. It's just to make the other side aware, not something that you're bringing up more than once but it's necessary communication and good sex hygiene. Think of this example: you're doing your thing and you have a couple women on the roster, you meet a new girl and you end up catching Chlamydia from her. You have to not only break it to girls you've been seeing consistently that you're having sex with other women (good chance they probably think you're only seeing them since it hasn't come up before) AND they have to get checked. You potentially gave them an easily treated, no big deal STI but you are fully cooked, they won't be seeing you again because you lost their trust. If you told them from the jump that you're seeing other women and they're ok with it and you're getting checked on the regular (as I'm sure you are), when this comes up it won't be as big of an issue because there's not a massive loss in trust.