Am I the jerk for wanting to tell my brother's fiance about the tracking app?

He secretly installed in her phone that he bought for her.

I'm a 22 year old female, my brother who's 27 is currently engaged to his fiance who's

25.

He bought her a new phone for Valentine's Day and asked my boyfriend who's trained in

computer software to install a hidden tracking app on the phone so his fiance won't see

it or notice it.

I overheard them talking about it and when I entered the room they went silent.

I waited till my brother left and then I talked to my boyfriend.

He denied having this conversation with my brother.

First, then admitted to installing the app on the phone.

I told him he and my brother were in the wrong because this is a huge breach of privacy.

He said he has nothing to do with it and advised me to stay out of it as well.

But I said I want to tell my brother's fiance.

My boyfriend argued with me about being nosy and intrusive but told me to stay out of it

and let them deal with their own issues.

But I thought that it was unfair to my future sister-in-law since she's the one working

paying the bills and rents and this is how she's treated.

My boyfriend told me to GTFO with this attitude and again said I should stay out of it because

it does not concern me in any way.

I don't know.

I feel horrible after hearing about what my brother did and since I have a good relationship

...