Pretty, to me, is completely unrelated to being taken seriously. Pretty, beautiful, cute, etc. are overlapping terms in my personal dictionary. A person can be one, more than one, or potentially all of them. I do use "cute" sometimes when referring to adult women, but I am usually thinking of what they are wearing as a component of how they look to me. As in "you look really cute" is another way to say "that's a cute outfit, and you look good in it".
I remember hearing one of my best friends refer to several young girls dressed for their Quinceanera as "lovely", and I thought that was the best descriptor she could have chosen. It seemed to imply something more than "pretty", but I find it difficult to describe what it is. It's as though "pretty" is on the surface, but "lovely" implies a glow from within. BTW, she is a linguist. She puts effort into finding the perfect word for the occasion.
I've been known to use the word "handsome" when referring to a woman, which does not mean I think she looks like a man. I believe this word pops into my head when I see a beautiful woman who has a strong, distinctive bone structure, if that makes any sense. Surface beauty, or prettiness, or cuteness may change or fade over time. A handsome woman will be handsome no matter how old she is, because the architecture will still be there.
And finally, I remember a pretty funny bit about all these terms from an episode of News Radio. I can't look for it now, but I'll post it if and when I find it.