I'll try to keep this fully SFW, but I think this needs to be said.
Just because you find a girl beautiful, doesn't mean you want to do dirty stuff with her.
Just because you find a girl's face cute, doesn't mean you want to cover it in "nasty stuff".
Just because you find a girl's hands extremely soft to the touch, doesn't mean you want her to use them to do *that*.
Just because you appreciate a girl's figure and maybe even compliment it, doesn't mean you are treating her as a sexual object, or wish to do so.
Here on /c/, we all wholesomely celebrate cuteness along with prettiness, no? Physical shape and traits (can) play a huge role in contributing to a girl's cuteness and prettiness. But it would seem to me that the very existence and behavior of this board proves that appreciating that can be done in a very, again, wholesome way.
Busty =/= ecchi, or lewd, or dirty. Big chests are almost universally considered attractive (I'm saying this as a justice supporter). So long as you are respectful and don't act like a pervert (which you clearly aren't, anon), I see no guilt in appreciating a full chest.
"She's so beautiful", "she has such a pretty face", "her hands are so soft and gentle". I don't see celebrating any of these traits as offensive, personally. So why not her bust, too?
She has a lovely chest. She fills her shirts really nicely. Her hugs must feel particularly motherly. Her proportions are very flattering.
I think those would be some nice compliments. There's a difference between this and intentionally staring, or compulsively trying to determine her cup size, or just spending *24/7* fantasizing about her using her breasts to do "that stuff" to your "thing".
correctly pointed out, her chest sure is not all she is. But if you call her "sweetest angel", her personality must mean a lot to you.
Don't feel bad if a, let's say _voluminous_ part of her beauty bewitches your eyes from time to time.