Sure you can. 
Frosting as filling is the default solution for those who don't want a special filling. 
For chocolate cake, I really like to layer raspberry preserves over (your favorite) frosting. This bi-color filling looks very pretty when the cake is plated. Also the raspberry flavor is more distinct this way, and the b/c doesn't get too soft (from the addition of the preserves).
Whipped chocolate ganache would also be a very tasty filling.
Here's a pretty comprehensive ganache thread:
(Has info on making, recipes, how to pour & smooth, and more.)
http://forum.cakecentral.com/cake-decorating-ftopict-397863-.html
Other filling suggestions for chocolate cake:
http://forum.cakecentral.com/cake-decorating-ftopicp-1826261.html
I'm sure your Mom will love the cake. 
Look forward to seeing pics. 
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