Thaaaaaank yoouuuuu. I still am trying to improve my body compositions and such. Thanks for the critism!

Breasts do not start at the neck, they start lower than that. Squeezing them together tightly (more than you've indicated in these images) could get the cleavage line higher than where they start, but not by that much.

The way you've drawn her breasts is actually fairly natural-looking - they're going to the sides as large breasts tend to do without rigid support. It's just that when breasts do that, they'll not have cleavage (or if they do, only a tiny bit). I think a small shadow between her breasts to indicate a gap should be enough to cement the fact that she has very large breasts, you don't need that massive line. In the large portraits in particular, it reads like a wound rather than cleavage anyway.