Way too strict with kids/what will happen?

My sophomore daughter is good friends with a senior girl she has known from her previous school. They both went to a small Christian elementary which went through 8th grade. They just really clicked as friends. This friend has a brother same age as my daughter who are also close kinda boyfriend/girlfriend without actually officially dating.

So my daughter has her sweet 16 party and invited this brother and sister. The mom would not allow them to go. The girl is a senior and soon will be 18. The mom does not approve of my daughter (who has never ever been in trouble). The boy could not come to my daughter's high school game even with a group of friends because this would be a date and he is not allowed to date. He is 15.

My daughter says she is very hurt by this - that this mom does not like her. The boy says he wants to bring her to his junior prom next year and my daughter wants to bring him to hers, but is worried his mom will not let him.

The girl is angry at her mom --- saying at 18 she will have a car and her mom will not be able to prevent them from visiting each other any more and they will get to see more of each other. Currently they were able to visit once at their house and only at youth group at church.

I worry for these kids (not that I can do anything about it) and my daughter being hurt by this mom. The daughter already started to have issues with her perfect grades going down.

What is the deal with this lady?