What are some security options for a small business?

My mother owns an antique store (mostly furniture, no jewellery or really small valuable pieces) and the last two Sundays she's been open she's had rather unsavoury characters come in, who she felt intended to rob her (but didnt when she kept talking to them and not letting them out of her sight). (Most stores on her street dont open on Sundays, its usually worthwhile for her to open).
Today a couple men came and waited in a van outside her store until she turned off her lights and sign, and THEN came in and asked if she was the owner and if she had any money to buy something off them. She is the type to like almost everyone, but she got extremely uncomfortable and scared by these people. She has a camera system in her store and the camera's monitor screen behind the sales counter for all to see that they're on camera. I worry more about someone hurting her b/c they think she has money, than someone stealing something. What can she do to protect herself?

wow; that is like asking how an entire industry
works!

a; she can hook up both inside and outside
computer cams.
b; she can volunteer that she uses a floor safe and that only Wells Fargo has the combination.
c; she can stop opening at odd hours;
all biz's need to review hours when
there are the most sales and stop
opening when sales are slow.
d; she can go to a banking environment;
whereby examples of goods are
on display but the actual inventory
is behind "hard" glass.

and more.

And she can hire a karate black belt to
be in the store when things seem most
risky.

Unfortunately she may have to stop opening on Sundays. Its sad to see how people try to take advantage of people whom they think are vulnerable. However if she insists on opening on Sundays she may need to start carrying a gun legally of course. When she has a permit to carry she will be allowed to keep the gun on her person and it may be a wise choice one day. Good luck I know you are concerned and I am glad to see that you are willing to help her.