The nurse offers the following solution to Juliet's predicament, after she has been the subject of a furious attack from her father:
Faith, here it is.
Romeo is banish'd; and all the world to nothing
That he dares ne'er come back to challenge you;
Or if he do, it needs must be by stealth.
Then, since the case so stands as now it doth,
I think it best you married with the County.
O, he's a lovely gentleman!
Romeo's a dishclout to him. An eagle, madam,
Hath not so green, so quick, so fair an eye
As Paris hath. Beshrew my very heart,
I think you are happy in this second match,
For it excels your first; or if it did not,
Your first is dead—or 'twere as good he were
As living here and you no use of him.
The nurse doesn't think of it as a betrayal, but in a way, it is. The nurse's advice - to marry Paris and forget about Romeo - is practical, and honest. But it doesn't acknowledge Juliet's passion, or the strength of the love she feels for Romeo, or indeed, that this love is such that marrying Paris and settling for second would be absolutely unthinkable.
Juliet's response - and the final moment in her relationship with the nurse (who will next see Juliet when she finds her apparently dead two mornings later) is bleak: her heart, and the nurse's, will be two separate things.
Thou and my bosom henceforth shall be twain.