I interpret this as a joke, but it does bring up something interesting: what was rendered as "cute" in the translation is デレ, or "dere"-- the same "dere" in both "tsundere" and "yandere".
"dere" doesn't mean "cute". It's a clipping of the ideophone デレデレ, or "dere-dere", which means something to the effect of "the feeling of being lovestruck". For example (and I figure you more or less know this), "tsundere" refers to a progression from "tsun-tsun" (ideophone, meaning something to the effect of "prickly" or "cold" in personality) to "dere-dere"-- or, an oscillation between the two
Keeping the above in mind (because I'm not going to try giving them a concise English equivalent), the title 徐々にデレ味が増してくツンデレギャル is more like "The Tsundere Gal Whose Dere-flavor Steadily Continues to Increase".