Well, it definitely falls within the boundaries of the lifestyle whatever you wish to call it. But why call it anything? Just do it.

There's no obligation to label yourselves, being happy with the activities is enough. Some people participate without ever considering themselves kinky. And as society slowly changes its norms, you can float in an out of the bell curve that is considered normal behavior.

If you want more, communicate about what interests you... or if your relationship is secure enough, just do it but talk about it afterwards... Consider having a safeword regardless of what you want to call it, so either of you can end an experimental activity that isn't working out.

PS. Don't assume a liking for the activities implies she's a submissive or would want a D/s relationship. The activities you described are all physical. What's going on in her mind during... does not have to be accompanied by a submissive mindset. And if it is, that doesn't mean she would be submissive in any context other than sexual. So if you do successfully escalate, don't assume it means you can change the dynamic between you.