Should I act against this?

I am in a situation where I am being lied to on a constant basis by someone who has a huge signifigance in my life. While I don’t want to take it to any other level because I care about this person I feel I am being pushed aside and disrespected. There is alot I could do to really turn the situation upside down. I didn’t get where I am in life by being dumb, but this person seems to think I am stupid. My question is, should I be offensive, or should I continue to just take it, since that is the obvious easier way to go? Should I let this kinda thing go, or show them precisely what they are dealing with?