Guys. The point of this question is not about yoga. And obviously it comes down to the girl making her own choice. The question here seems to be more of do these kinds of clothing, when worn on women, have any affect on you as a male, because of the tighter nature of the clothes.
The simple answer for most men will be yes. How a woman dresses, be it tight clothing, revealing clothing, low cut/short clothing, etc.. is going to have an affect on most men. Period.
If we want to get into the blame game, both men and women are responsible. Men are responsible to do their best to control their thoughts and where their eyes go, but women are also responsible for how much they reveal about their bodies and display it. Neither gender is exempt, though many times people like to put alllll the blame on one or the other.
In reality the bible says that if someone is weak and struggling with an issue it is the responsibility of the person that may cause the stumble to change, at least in the presence of the weaker person. Which is the opposite of what most Christians seem to believe. The person struggling is already doing their part, which is why they are in a struggle.
Also there is the consideration that the vast majority of guys are not trying to contain their lust. If a woman walks around in clothes that may get a mans attention on her body, you are responsible for causing people to lust after you. Granted unless you want to go Muslim and wear head to toe garb, then you have a risk of this anyways. But dressing in a manner that increases that chance by putting emphasis on your body falls on you.
The issue always falls onto 'Christian men shouldn't lust'. But even if we eliminated lust among Christian men, the bible still speaks of dressing modestly. And you still have the majority of non-Christian men willing and seeking to lust, and providing that opportunity as a Christian still falls on you i believe.