Explain this quote from Macbeth: "Glamis thou art, and Cawdor; and shalt be what thou art promised" to show Lady Macbeth's ambition?

Lady Macbeth speaks these lines in Act I after reading a
message from her husband, Macbeth. Earlier in Act I, Macbeth and his friend and fellow
military leader, Banquo, come across three witches out on the heath after a battle. The
witches give both men prophecies; Macbeth is told he will become Thane of Cawdor and
King of Scotland. Minutes later, some men sent by the current King, Duncan, inform
Macbeth he has been named Thane of Cawdor after the former thane was found to be a
traitor (he will be executed and his position reassigned by the monarch). Following this
encounter, Macbeth sends a message ahead to his wife back at their castle at Inverness,
and in this note, he reveals the prophecies to her. What we see in this quote is Lady
Macbeth's immediate reaction to this message.

Lady Macbeth
first repeats information we already know: that Macbeth is now both Thane of Glamis (his
old title) and Thane of Cawdor (his new title). Lady Macbeth then states that Macbeth
"shalt be/ What thou art promised" (I.v.16-17). This means that Lady Macbeth takes the
prophecy at its word and implies that she is willing to do whatever it takes to ensure
that it does indeed come true. Lady Macbeth's choice of words here - "shalt be" --
reflects her belief that either his position as king is guaranteed by fate/destiny or
that it will be because he, she, or both he and she will make it so. This hearkens back
to a comment Macbeth makes in Act I, scene iii, after hearing the prophecies: "the
greatest is behind" (I.iii.123). That statement indicates that Macbeth believes the
prediction that he will be "king hereafter" is actually
true. 

Lady Macbeth's comment in these lines indicates that
she has ambition in the sense that she wants her husband to be king and she wants to be
queen. It is somewhat unclear what her personal ambitions are, but it is clear that she
wants her husband to be in power, and, of course, she will benefit from that power, as
well. Immediately after these lines, Lady Macbeth continues her famous soliloquy, in
which she reveals her fear that Macbeth is too kind and too meek to actually go through
with murdering the king in order to quickly ensure his own rise to the throne. She also
reveals more about her own ambition in the part of the soliloquy where she laments that
she is a woman and wishes to rid herself of her feminine qualities so she could simply
kill Duncan herself. This indicates that her ambition for power is strong but she also
is aware of the limitations placed on her by her gender. The only way her own ambition
can be satisfied is through Macbeth, so she must support his rise to power to have
access to her own.