You're most certainly allowed to edit it. That's one of the cornerstones of all free and open software. However, you must also make your edited version available as source code under the same terms as the original library. That's one of the cornerstones of copyleft licenses (such as the Lesser GPL). Use the software in a free manner, and in return give any modifications/improvements back to the community.
Since Alice seems to be a library, and assuming that you will use your modified version of it as a library, you can likely license the rest of your application in any way you like. See section 4: https://www.gnu.org/licenses/lgpl.html
OSS licenses do not (normally? ever?) restrict you from charging money for the software. But you do sometimes have to provide some or all of the source code for free (and under a particular license) as well.