Spanish Seduction

Two days ago I met this Spanish girl. We chatted for a bit, I found out she moved here a few months ago and will be staying till some time in the summer. She's learning English and is living with a family while looking after their kids. We carried on talking, I got her number and I wound up showing her how to complete an English paper she was writing (I made her work for it). Immediately afterwards, I left, intending to call/text her later.

Last night I started texting her with the intent to get her over for a movie. She then tells me she's sorry she for forgot to tell me, but she's got a boyfriend. Here's how the text reads:

Me: Did you finish the rest of those questions?
Her:Yes thanks
Me: That will be £500 for the tutoring sessions
Her: Lol
Me: I'm serious, I don't teach for free.
Her: Okay okay, I wont disturb you more next day XD
Me: How about this instead. What are you doing tomorrow evening.
Her: Mmmm sorry I didn't tell you yesterday but I have a boyfriend. You are very kind but maybe you have the wrong idea sorry. I didn't want to be rude yesterday.
Me: Your boyfriend doesn't know does he?
Her: Eh no
Me: I don't see a problem. Do you see a problem?
Her: mmmmmm Its not a problem but....
Me: All I'm offering is a good time, good company and a good movie (in English, none of that Spanish crap
Her: But probably my boyfriend doesn't like that. And he's not in Spain. He lives her as well and he is English too.
Me: What he doesn't know wont kill him
Her: lol
Me: It'll be our own little secret
Her: Eh no thanks. I'm okay
Me: Suit yourself
Her: ????

The impression I get from this series of text is that her only objection to any kind of encounter is the fact that her boyfriend lives locally. And with her time here short, I doubt she plans on staying committed to anything. As far as I'm concerned, she's up for grabs.

What I would like to know is, what did I do wrong, what I did right, how I can improve, and what can I do next.

Lets get me laid.

What you did right is showing interest.
You can improve by understanding women are non confrontational by nature and will try to let you down easy.
What you are doing (very) wrong, besides failing to catch a hint (more like 3 hints), is trying to verbally convince a woman to cheat. Whether or not she has a boyfriend is irrelevant. If she does but were also legitimately into you, she would shut the fuck up about it, instead of shoving him in your face every other text.
She's not saying "I'm taken". She's saying "I'm not interested".

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She is not interested in you, at all. "i have a boyfriend" is a red flag. She might be shy, she might be playing hard to get, but then she tolled you again and again NO.

Let her go.

I keep getting into these situations where I talk to a girl, get her number, call her/ text her but she doesn't pick up or respond.

Positives
I'm getting numbers, I'm approaching frequently, I am direct, I qualify and I have no problem with rejections.

Negatives
Too many times I get a number and when I try to follow up, it leads no where. What am I doing wrong? what variables am I missing? whats wrong with my interactions? what should I improve on?

Its getting frustrating to keep hitting the same road block