I am really sorry you go through this situation yourself.
Unfortulately, as a teenager, you are helpless in this situation. You can express your trouble, it is unlikely to change anything to their decisions, but why not, if you fell you need to say someone.
With all due respect to your mother,
This sort of situation is a moral dilemna. We have here three adults, who are catholics, so not completly ignorant of the issues they created/managed, but deliberatly choose an immoral path. I don’t prejude of course of how much their thinking is morally educated.
I will try to explain some aspects for your conscience formation.
First, the only moral way to give life to children, is from natural intercourse. And because we are christians and believe to covenant of God, this should take place in sacramental marriage.
Others sexual relationships outside of marriage, including of the same-sex one, is not what God call us.
So creating children through artificial technics such as artificial insemination, IVF with or without external donors is a sin and is a prejudice against the dignity of the children conceive, and even the dignity of the parents.
Of course, surrogacy which dissociated the maternity of the biological mother and the pregnant one is gravely evil.
Contracts, payments for processures and mothers, unkown genitors are others natural wrongs against the principle of the body indisponibility. It is making life giving a business. These principle is garantees in some countries, but unkown in others.
Ensuring that all the embryos are given a chance to life in all circunstances,- which is also practically impossible in some cases is not the only moral aspect to consider.
We are still in a moral dilemna and the Church recognize we cannot solve this dilemna create by acts that should never had happened. Given the children to others couples is possible but will create others disorders, because the child who will be born will have a more explosed biologicals origins.
In Dignitas personae instruction, paragraph 19, the Church currently recognize there is no moral solution to an immoral situation : a " situation of injustice which in fact cannot be resolved."
The immoral situation is the deliberate freezing of embryos
There is no acceptable solution.
Giving them to laboratory research is immoral
Giving them to others people/couples is inacceptable because men and women can only become parents by their wife/husband, it will only give an “moral” exit to a voluntary immoral situation, and IVF + embryo transfert is immoral in itself.
permanently let them stay frozen is something close to therapeutic acharnment.
the only remaining solution is to destroy them, even if the killing in itself cannot be approved.
Some people try to save the maximum of embryos at all costs, as a prolife conviction. It is only their feeling, but not what the Church mandate.
Implanting 2 of the 3 embryos is not more moral than just implanting one. More, on medical level only twin pregnancy is more complicated.