Privacy or not

So my mother in law came today and we talked about setting the wedding ..anyway she said in front me I check my son who is my fiancé phone and I read his conversation with you ...at that point I just felt awkward and I just stood frozen because I felt she intrude our privacy .. since today I just talked to him like hey how r u .. what should I do ?! And what she does is it right ?! What do you guys think