“Well mom, you are right, I am going to join the Marines instead!”
Yes, these days, that may in fact change her tune.
jstreets - if possible, you may want to try to visit a seminary. I spent some time in formation myself before discerning otherwise. One third of my classmates were converts.
One in particular came from a Calvinist background and his father used to send him anti-Catholic tracts, the Westminster Confession (with the reference to the pope as the “anti-Christ” marked with a highliter), newspaper clippings about priest scandals. It was
NOT an easy thing for him to deal with.
Maybe in going for a visit, you can meet some other folks who have been dealing with different degrees of parental opposition and discuss with them how they handle it.
This much I would also advise - avoid fighting about it. It will lead to stress for both of you, strain charity, lead to pride, and and lead to some possible occasions of sins against the fourth commandment. I fought with my mom quite a bit about it at one point. I was not wrong to want to go. I was not right to be so proud and argue with my mother.
Remember: A lot more men go to seminary than get ordained. This isn’t failure, it is a success of the discernment process. MANY men (your truly) have spent time in the seminary, didn’t get ordained, don’t regret it, and are glad for the time there. I made some great friends who ARE priests now, I learned a lot, and I now own my own cassocks for when I serve at liturgy! (Still fits!)
So perhaps better also to frame this desire to go to seminary in terms of “I want to have this college experience, in this environment, not everyone gets ordained, but it is a good experience.” (which is true) rather than asserting that you ARE going to go become a priest and “she better accept that reaility” (Which is how I did it. Though, she did not accept it, I did not become a priest, and we waisted a lot of hours fighting, and damaged our relationship terribly for a few years.)
Ordination for you is probably at least 7 years away - if it is even that close (some programs take longer).
People sometimes don’t understand the subtle yet BIG difference between going to seminary and becoming a priest. You aren’t “becoming a priest” until the day you enter a church to be ordained by a bishop. If possible, help her to see that, if and when you do discuss it.