NO to buying a house together and merging families. not with someone at just 9 months sober. not because it's "now or never". IF your relationship is sturdy, and IF her recovery remains solid, there is NO rush to do anything different.
NO she is not "healed" at 9 months sober. check in with that when she has about THREE years sober. the first year is really just learning how not to drink, how to get thru seasons and holidays and not drink. how to deal with jobs and children and not drink. how to get thru a bad day and not drink. car repairs. roof leaks. sick cats. and not drink.
a mortgage is a BIG deal. you both would be equally responsible. and there is no "easy" out if things don't work out. asking children to "merge" their lives with another family is a big deal. HER children have only had a sober mom for a few months. and she isn't all THERE yet. they've had enough upheaval.