I’ve been away for a bit, and saw your posting this morning. First of all, yes you are welcome at Mass. Everyone is welcome to assist at Mass. Not just those who approach the altar for communion. By attending you may make yourself availible to the Graces God gives to each of us which strengthen our faith.
Unfortunatly what your mother said about the priest and nuns is not clear. There are people who don’t like police, or people with long hair, sometimes it is because of something that happened in their past, other times there is no reason. An individual priest may have snapped at her once when she was a kid, who knows if she did not share it with you. But the reality is that the priest when he is preforming the rites that the Church gives us in the Sacraments is not acting on his own authority, it is Jesus who acts upon our souls through the Sacrament. It is Jesus who gave us the Sacrament, and His priesthood that the individual priest exercises, not the priest’s own personal posession. If the priest is a nice person, or an old grouch, it does not matter when it comes to the graces of Sacrament that he dispenses.
I’d say, go to Mass, discover what it is that the Church teaches, remember that we are all humans, and one of the best things we can do for ourselves is to live each day with the intent of improving ourselves. Through our own personal prayer life, which can include prayers in our own words, Mass, and the other Sacraments, as well as any of the hundreds of approved devotions of the Church, we can do this. Don’t let the fact that not everyone puts an effort into changing and improving their lives through the Sacraments stop you from investigating how you can benefit from living life as a Catholic