At her age of 58 pathological migration of teeth is common due to periodontal disease. After thorough evaluation by the dentist, u must undergo treatment for gums preferably with the help of the Diode lasers which we have been using since almost 15 years with amazing results. After stabilising all teeth with proper treatments we can think of smile designing to close the gaps. Closure of gaps can be done with composite materials or porcelain Laminates or crown and bridge work. The line of treatment can only be decided after careful evaluation and x-rays. Feel free to consult Laser Smile Care. God bless.
Before deciding form of treatment a full mouth x-ray that's an OPG would be required. Tooth movement may occur due to various reasons like periodontitis that's gum infection or swelling or due to missing teeth. The absence of teeth causes the other teeth to move trying to close the space created by missing teeth. Blackening of Gums maybe due to melanin deposition which is quite natural.
A personal consultation would be prudent.