Glock.

her crown

A small alligator (deters purse snatching)

A mirror, lipstick, face powder, tissues, and a can of mace.

Lip balm.

According to an artical in The Daily Telegraph in 2012. One royal biographer says that there is a lipstick, a mirror and a new £5 note. Specifically for donation on those days when the Queen goes to church.
All the bags aparantly have a discreet hook so that they can be hung discreetly under tables.
A Lady in waiting who accompanies the Queen on official visits, has a bag containing : Reading glasses; mint lozenges; a fountain pen and the aforementioned folded £5 note.

I did read somewhere that the Queen doesn't carry anything in her bags.
Although she is quite fastidious in ensuring that she has just about anything she could need on standby via a lady in waiting.

...and a very well-groomed and well-behaved cat.

A wedge of sharp cheddar?

Pic of Charles.

Emergency replacement faces...

Breath mints tissue and maybe a taser

A handkerchief or mirror for sure.

With a posh accent:

Dear Sir!! That is a question no gentleman asks!!

Lmbo!! Just kidding... She probably keeps a handkerchief.... A mirror... A lipstick...

Idk :) maybe it's empty :)

Taser

That hat tho..
I would rock that hat *nods reassuringly*

A can of Shut-the-F***-Up! to spray on her husband when he starts saying controversial and offensive things...😵