Here is the problem with what she is wearing:
Women who dress like this do so to get attention. Then they fall all over the first attractive (either through physical looks or having $$, or something else she wants) man who gives them the attention that they are seeking. If some of the attention that they receive is from a man that they regard as being unattractive, the same woman will complain about sexual harassment from that man and about how accusing women of “asking for it” is blaming the victim. This creates all kinds of HR and legal liability.
The other women in the office who aren’t dressing like this accuse the woman of trying to sleep her way to the top, or they get angry that the men in the office are pigs. Women are catty like that.
I once had a woman who was dressed in a skimpy outfit get mad at me when I looked at her. She was confronting me, then her meathead boyfriend came over and wanted to fight. I refused, and he threatened to drag me outside for a beating. Luckily, he backed down before he got himself into more trouble than he would know what to do with and wound up costing me some legal fees.
Have a dress code, enforce it, and this all goes away. Tits are fun to look at and I am definitely a fan, but they are poison to a professional workplace. Send her and her cleavage home.