Were you the life tenant and the remainderman?
If so, you owned the property in fee simple as a result of the doctrine of merger. Consequently, you did not acquire the home at your mother's death but at the time of the transfer.
Regardless, if you owned the home in severalty (you were the sole owner) since 2007 and used the home as your main residence, you can take advantage of the home sale exclusion.
See https://www.irs.gov/taxtopics/tc701
You need to provide more details about the nature of this transaction.
