Are you asking how best to move on Alejandra? And wondering what happened that both Daniel and Alejandra stopped responding after your 19 yr old gf got Alj's headphones to return to her thru Daniel? It's obvious that your gf (who you don't name) is very hurt and feels helpless, so perhaps D & A are holding back out of consideration for her. And if that's true, then they may be expecting you to clear up your relationship before you make more advances toward Alejandra. That sounds fair, since the younger girl brought you as her "date."
One major issue in gay & lesbian circles is that many lesbians don't see why they should follow courtship customs that straight people believe in, so preserving strict partner loyalty is no big moral imperative and everyone should be free to make her own rules for what is right and wrong--so you toned down your flirting in front of your gf. The problem is, having all that freedom to do what suits yourself the best makes lots of jealousy problems happen. Younger people are often more idealistic and absolute about their morals, and she's also the one getting hurt by the somewhat older women.
It is considered normal among gay men that 6 months is the ending point for sexual affairs, so there will be a commitment challenge at around that point. I don't know if that's considered normal among some lesbian groups or not, and I certainly don't know anything about specifically Mexican lesbian relating customs. But it's possible that both Daniel and Alejandra might expect that you could be ready to quit your affair with your younger gf. So they're expecting you to act next.
That means you're faced with how to act now: to tell your Chiquita in a kind and understanding way that you're not in love with her as much as you were before (tho I have no idea what words would fit for you), so you need to move on, and you know you're hurting her and you're sorry that your heart isn't in it anymore, she's still a wonderful girl and you'll always tell people how great she is, etc. Or you try to fade away without any direct words, and without accepting the moral responsibility for ending what has meant a lot to her (because as you said, she might admire you a lot and idealize you as her role model). It takes moral courage to admit that you're doing something that hurts someone that loves you.
This is a thorny matter in lesbian circles, perhaps, because it sure is for gays: When one partner is and KNOWS she is more attractive to potential partners than the other partner, she has more "sexual power" (for gays it's pure physical beauty and charisma, and it seems to be in your situation too, because of how you write about Alejandra's sex appeal). I've heard of gay and lesbian "alpha-wolves" justifying dumping their "beta-wolf" partners by pointing out their higher desirability in the lover-scene, as a blatant rejection of the moral rules they don't want to take over from the straight courtship scene--and the rejected person usually remembers the sting of that rejection for the rest of her (or his) life. IF you do express your rejection as justified by your greater age, experience, sophistication and/or feminine appeal, you will deliver a direct blow to her self-image, so I advise against that. But you probably already didn't want to obviously "put her down."
If you say nothing about why you're sliding off to pursue somebody else, then she's fairly likely to assume it is because you don't care about her as much as she thought you did, and she's likely to give credit to all of her negative thoughts and feelings about herself. You might be able to ignore the awareness that you're making her very likely to trash her own self-esteem, but you're leaving her to make up her own justification for why she feels so bad from being rejected, when you could be giving her words that help her keep up her self-respect.
So I'd advise you to take the blame onto yourself for wanting to move on, and to tell her many of the really good experiences you've had with her and the many good parts of her character and beauty. It might be easier for you to do this in a letter, a "Dear Chiquita" goodbye with praise and fondness and what you got that was special to you during your time together. You put the blame on yourself, and just say you're not into settling down with one person yet. You basically want to help her keep the self-esteem you raised in her when you made her your girlfriend.
Does this make sense to you? Morality in this case does not mean saying "Yes, I did you wrong," but it means instead admitting "Yes I don't want to be exclusive anymore and I don't want to hurt you by pursuing somebody else, so I'm setting you free to do your own thing, even though I still like you and am attracted to you a lot."