It's quite simple. There's no universal right to sex, in a committed relationship or not. There's also nothing forcing him to remain. If he'd agreed from the beginning to wait until she's ready, and he did, then he should simply wait. He's the one breaking what they both agreed to, not she. She isn't forcing him to anything, just asking to keep his word, which she trusted him to do in the first place. If his dick is too itchy for him to do exactly that, then, well, she was right to abstain and perhaps should look for a better party.

Also, three months is not long. There are people who take years. Again, if he cannot keep his word, then perhaps he should go to a brothel or fap off, and not be looking for, like, any relationship.

It's in fact more about trust than sex.