If a girl is goood and conservative Muslim girl have a relation with a man and they have a intention to get marry in future. This girl was vergin and untouched. If the boyfriend want to touched her will she denay? Does she let him touch her breast easily?

She would deny and say no, since they are not married

Just to add... if her boyfriend respects her, he will also respect her beliefs and not ask her to allow something she does not want to do.

Regardless if she deny are allow to touch it is harm, Thanks.

Ya touching a girl before marriage is Forbidden and it should be avoided...