It's literally just "If I masturbate I'll get addicted to it and I'll let myself and my future spouse down" in fewer words 😔
So, as a woman who has been where this girl is rn, is married to a man, and was sexually active with this man prior to the marriage, let's clear a few things up:
1) There is no guaranteed future spouse or "the one" for everyone. Churches may tell you this and even secular materials may tell you this, but it is not true.
2) Marriage and sexual activity often go together, but they do not have to, and a healthy marriage depends on way more than just sex.
3) Even if you do end up getting married in the future, you are not cheating on your future spouse by masturbating or having sex before you meet said future spouse.
4) Whatever you do and think about to pleasure yourself are entirely private and have zero bearing on the health of your future relationships--except, of course, perhaps in a positive way: if you learn what you like ahead of time, you'll be able to teach that to your partner, and you'll enjoy sex more, and by extension so will they!
5) You will not get "addicted" to masturbation just because you enjoy it, and you're not addicted just because you do it multiple times a day. There really is no such thing as masturbation addiction.
6) There also really is no such thing as porn addiction.
7) People who fear such a thing happening to them or who believe they are in that position are often found to have been conditioned to feel that way due to sex-negative religious upbringings. Usually what's found is that their masturbation frequency/level of porn consumption/etc is entirely normal.
8) There is such a thing as compulsive masturbation or compulsive porn consumption--when you do either or both to the point that it's getting in the way of you being able to be present in your daily activities and relationships--but usually there is some root cause, like avoidance of deep feelings or problems. The same thing can happen with any activity, like food, video games, or work.
9) Masturbating does not leave you incapable of receiving sexual satisfaction from or desiring sex with another person.
10) Same thing with consuming porn, by the way.
11) And on that note, using porn within a relationship doesn't necessarily mean you are cheating or that you are dissatisfied with your partner. But knowing their partner is doing that hits differently for different people. What really seems to have the most negative effect is discovering secret usage despite setting boundaries about it ahead of time. Checking in with each other to make sure you're on the same page is important.
12) Using toys/vibrators to masturbate and even during partnered sex is entirely normal, healthy, and sometimes necessary for some people, especially those who have a clitoris. If your partner feels jealous or inadequate because of that, it's because of their own insecurities and hangups, not because you are doing anything wrong.