There are security issues.
You are sharing bandwidth so you will notice a slowdown.
You are probably violating your ISP's Terms Of Service.

Pooh Bear

Thanks, and what type of security issues are we at risk of here ?
Salbwil

depends, if she is on your network sharing it then it could be possible that she has full access to your pc/ network.

Do you know what data is flowing thru your network??
Normal web surfing and email wouldn't cause much of a slowdown.
But file sharing apps could cause a huge slowdown.
Illegal file sharing now accounts for over 1/3 of all internet traffic.

Also, does she use safe surfing practices.
If she gets a virus or spyware, you could get it too.
If she gives someone access to her computer,
then they also have access to your network,
and possibly access to your computer.

And she could share network log in info with her friends.
They could drive up in front of your house and use your network.
And the question remains, what are they downloading.

Yep, lots of security issues when sharing a network connection.

Pooh Bear

She's a librarian, not that that means anything, but I really don't think she'd be inclined to "share " information with friends, etc. I do think, however that maybe I should ask her to let me know if any of my information shows up on her computer........I know my ignorance is showing here, but is that possible ?
Thanks again,
salbwil

you are being very trusting and in these days of stolen identity that unfortunately is NOT a good thing. It is possible for your system to be accessed and not just by her, if she has her wireless network set up insecurely with out proper security protocols set then any one near your house even some one driving by can spot that you have an open unsecured network and they can use their pc to jump right on to yours.
This driving by looking for open networks is called war chalking, they even have codes they will write in chalk on side walks to let others know this house is wide open, they have websites they list addresses on for houses with open networks!
war-chalking and more

Please be very careful your kindness could cost you dearly, and not necessarily by the nice librarian but by someone that found your open network.

here are some good helpful links on understanding and implementing secure networks.
Securing A Wireless Network

few easy steps

a nice slide show of the steps
Photos: How to secure your home wireless network

and just as important change the default user name and password on the router!