There are several issues to discern here, but the
essence of my post can be summarised into one sentence:
Love is not about looking at each other; but looking
together at one collective direction.
When a couple shares a parallel view of their individual definition
of love, chances are, you will find conflicts with regards to
choice, perception and view of life & relationship because in a
parallel line, the lines will never meet at point X.
This is not an issue of what you want her to know because that
depends largely on the sort of wisdom she has. To employ dialogue
and communication to alter her fundamental belief about love is as
challenging as changing one's personality.
To understand your plight, we have to review the basic - our
needs.
21 years old girl and a 26 years old guy: surely the age difference
would suggest proportionate widening of expectation, due to
segmenting of separate phases in our life. You can't expect a woman
of her age to perceive love and relationship the way you do?
The theory of love needs are often logical to self, but illogical
to others. Woman will never understand man's fascination about
blowjob and boobs. And the problem is that they don't need to -
they only need to know that it exist. Similarly, you don't need to
understand why she is giving you trash because you will probably
not know anyway - you just have to know the this is the woman you
accepted as girlfriend three years back... this is your choice.
(CloUdiSm first law of Love) 
I wholeheartedly agree that you are a responsible
guy.
But your insecured girlfriend, being your woman, probably felt
neglected due to your lack of presence in the relationship. Such
short-term 'needs' might be 'nonsensical', but certainly they do
qualify as a need, don't they? (As mentioned in the above
paragraph).
Some woman loves a man like you and they don't mind enduring that
emotional sacrifice, knowing that whatever you are doing right now,
it's for your future together and they so love a responsible man
like yourself. But there are also a group of woman who cherish and
appreciate spending quality time with their other half, much more
than you telling them you are going to spent the next year working
hard (likely to be at the expense of your relationship) for a
better home (CloUdiSm Elemental theory - Earth vs Water)
And I can tell you they are both equally right - just that from
where they are standing, they are looking at love from different
angles.
I remember an old story in the papers, where this man worked his
guts out because he always felt the importance of finance and the
ability to provide for the family. Then he read, also in the
papers, about the story of this man who regretted not showing
affection to his significant other when she was alive and now he
can only spent his time at her grave.
Inspired by this article, he drove to Malaysia, with a bouquet of
flower - wanting to give his wife a surprise and he end up getting
a bigger surprise.
He gave his wife the flower and told her that he loves her. She
cried incessantly, not only just because she was touched by his
action, but also, if he has arrive an hour later, she would have
committed suicide because she thought that her husband no longer
loved her.
***
Love and career are often mutually exclusive. The
one with the high flying career might not have good relationship,
while the one with the humble job might have very fulfilling
ones.
Everything depends on where you place your priority.
In love, every mote of individualism devours away mutual strength
in a relationship. This is decided by freewill... by our choice in
life. If you have decided that your career is the most important
aspect of your life currently and you are able to do away with your
relationship to advance further - you will probably do it.
This is your choice - your woman, having separate sets of needs,
would probably have to go.
When you try hanging on both realms, frustration builds up from
parallel views that would never meet and eventually things become
sour and will implode unsightly.
Either you truly convince her to look from where you are looking or
you lower yourself to view from her perception because
ultimately:
Love is not about looking at each other; but looking
together at one collective direction.
Cheers
