My sister isn't very internet savvy, and did not e-file her taxes on time. I just found out on April 27, and finished them for her and e-filed them. She will get a refund, but will she be penalized for filing late?

Yes, if she owed tax on her return, she will pay interest and penalty. But it will be just a few dollars. If she had a refund, she will not pay any penalty.

MukatA has it right.

Same applies for the state: penalties and interest are due if she owed taxes. If she has a refund coming, there is NO penalty for filing late.

How and where do we get the forms to file late

Go to Internal Revenue Service
On the left side, select the form or click More Form and Publications.

You can also download them from Home - 1040.com.