Boy, that is a rotten situation to be in. I'm so sorry that your mom is dependent on him for money and seems to have no consideration for your feelings or your fathers for that matter.

Do your mom and dad talk at all? Can your dad tell her that her b/f is not welcome? You have every right to exclude them both from the party if she is not willing to come alone. Blended families do not always blend.....it's unfortunate but the way it is sometimes.

Is it possible to come up with the money for your mom to attend so she can leave her b/f home? Why would someone want to horn in on something when they know they are not welcome? That just doesn't make sense to me unless they are trying to make a point at any cost and at your expense (emotionally).

I do hope you can find a way through all this.

Take good care!