My mom died. Now my dad is referring my mom as his ex to his friends/relatives. Is this correct?

he shouldnt be referring her as an ex, thats kind of rude and disrespectful

No, he shouldn't be referring to her that way. He should call her his "late wife," or better yet, by her name.

actually, the correct term is former president, not ex-president. When referring to his wife to friends and relatives, he should just use her name, as they presumably know she is deceased. Ex implies either he or she dumped the other and I would agree it seems disrespectful of the years they had together. She would also be considered his first (or whatever number) wife or former wife.

My grandmother died over a year ago, and my grandfather still refers to her as his wife. To me, personally, i dont think its right to refer to her as his ex. Sit down with him and ask him why he does that and then ask him if he could stop because it makes you sad.