What does "Take the disguise" mean?

Solution 1:

No! The verb take has various uses and senses. She took the clothes of an old woman would have the sense you mean, but take is not infrequently used 'delexically' - as a sort of 'dummy', bleached-of-semantic-content verb; the expressions where this happens are really fixed idioms. Examples are:

He took ( / had) a bath.

Take the next right.

Do you feel like taking a walk?

She took the disguise of an old woman (ie she disguised herself as an old woman).

DNA actually takes the form of a double helix.

But note that the delexical - lexical distinction can get blurry:

Sauron took the form of a mighty warrior clothed in armour.

Here, 'take the form' implies an electing to exist in this form at this time, so take is not just a verb bleached of meaning here. This is true also with 'take the disguise (of)'.