Sanseveria aka Snake Plant or Mother In Law's Tongue grows best in a sandy soil, direct sunlight, and minimal water.

Pot is too big!

1818, this plant is suffering from those 6 months without water, the leaves down on the side of the pot are severely dessicated. First thing to do is cut all those wilted leaves off as close to the rhizome or soil level as possible. If you want to leave the plant in the pot for now, pry that saucer off the bottom of it so it can drain properly. Put a loose saucer underneath it if necessary. Next, water and see if it actually wets the root ball rather than running down cracks in the soil. Also, when the root ball goes bone dry it shrinks away from sides of the pot, so check if water is escaping there too, rather than soaking the soil. If the mix isn't being thoroughly wetted, its turned into a brick and it's necessary to break it up with your hands... not easy.

Long-term, my suggestion is to do your best with it until spring and then unpot, break up the root ball and extract the plants and rhizomes with as many roots as possible. Repot with only the best, healthiest pieces into a pot that will just contain the rhizomes. You can trim rhizomes to 3 or 4 inches per plant.

Use a crunchy mix that drains well, one that does not contain sand. The bark mix popular on this site is okay for sansevierias, add an extra portion of perlite. If you use a commercial peat-based mix, add perlite in a 50/50 proportion. A commercial cactus mix is better, many growers still add some perlite.

Don't water in sips, water fully when the top inch or two of soil mix is dry. You want to see water coming out of the drain holes.

Post if you have more questions.

Russ

By the way, you might separate a plant or two and pot separately as backup insurance against total loss of your big plant. You could also take leaf cuttings which will produce new plants. they would essentially be the same plant your grandmother had.

I have a 60+ old peperomia of my grandparent's that I'd hate to lose, so I keep multiple plants of it just in case. Let me know if you need help with leaf cuttings.

Russ

Aha, interesting! So what changed when you moved into your present home? Did you start treating it better than at the other location? Watering more often?

The only thing that can cause such devastating wilting is either no water for a very extended time, or over-watering which rotted the roots and plants can no longer take up water. Essentially causes the same symptoms as severe dryness.

I would still do the water test to see if the root ball has turned into a brick.

Russ

You'll need to find a larger size of perlite (not rocks). I buy size 2 at the organic gardening/hydroponic store here in town. The size two seems big at first but breaks into smaller pieces very easily (dont break it apart on purpose though, you want it in bigger pieces.)

Be sure to sift and rinse it, otherwise the dust on it can gather at the bottom of your pot and create a swamp that stays soggy, like sand does.

I would like to warn you against purchasing the Miracle Grow brand of perlite. It's like they used all the good pieces and bagged up all the fines to pass off as perlite. It just turns into a mushy, soggy mess unless you sift it and then you can only use ~1/8 of the bag as the rest are fine particles and unusable. Total rip off.

As Russ said, you'll need at least 50% of the mix to be perlite (you can use perlite mixed with chicken grit [crushed granite] to make up this half of the mix but the grit can get very heavy if it's a large container) combined with 50% or less of the cacti and succulent mix you buy, if it's based on peat (sphagnum peat or coco peat, which is what most people think of when they think of potting soil, very small organic materials).

Little jab: and I thought my pictures were bad! If you're using a phone, you should be able to click on the item you want it to focus on and it'll focus for you.