If this is your first HC char, well, you took on a char which gets some danger to die at late NM and Hell dificulties. Don't get me wrong, sorceress are very good if you know how to handle them, but a wrong teleport or bad tactics at gloams and that's it.
Builds that have much higher chance of beating HC Hell difficulty are builds like fishymancer (necromancer using skellies), concentrate barbarian (with some good crowd control skills), cheesadin (paladin using blessed hammer and concentration) and other. The fishymancer and the cheesadin especially are good, since they don't rely very much in items, so untwinked is not a problem.
Now, notes on HC: survival is everything. While in Softcore one of the most important things is to get as powerfull as you can, in Hardcore the most important thing is to survive. When you see a pack, you don't inmediatly run to them to slaughter them, you first see the stats of the boss and if it's dangerous you have to learn to "divide and conquer", life charms are especially good here, resists are a must, DR is a wonderfull thing to have. Power comes second to Survival in HC.
As a HC Sorceress, you have to carefully plan what you want to use (which by being untwinked makes it kinda hard), but don't go very high on Str, and since as untwinked you don't have an idea of what shield you can come across, you can't plan your required dex for max block. I would leave dex alone and go all over vitality, as for energy, well, since you don't mention the build you will use, I wouldn't put much points into energy, that's why there are mana pots.
Use every possible tool in the toolbox (especially true for HC untwinked chars), for example: crafts. Caster or Safe items are very good (very very good) for an untwinked sorc, grab blue armor and sell them so you can gamble for circlets, rings and amulets, if you lack resists, hold your gems (including skulls) and cube them up to perfect (6 gems of every kind + amulet= resist all amulet). Low level runewords such as ancient's pledge (ral+ort+tal, for resists), Leaf (Tir + Ral, for a nice boost to the fire tree), Lore (Ort + Sol, for a boost to skills, lightning skills and even mana), Rhyme (Shael + Eth, excellent shield!, increases chance to block, nice boost to all resists, faster block rate, good regenerate mana and even cannot be frozen, impressive for so cheap runes) are very good and the runes can be easily gotten from game of some countess runs. Merc can also get hold of things like strength (Amn + Tir, fair ED, 7% life leech and 25% chance of CB, excellent for boss running and it also adds nice +str) and Honor (Amn + El + Ith + Tir + Sol, nice ED, adds to min/max damage, 7% life leech, 25% chance to deadly strike and even adds to skills, excellent for some cheap runes).
Keep in mind all these details, and especially, don't go to Rambo attitude: don't run into crowds, as a sorc use teleport to your advantage, use static field, learn to position your merc by using teleport, divide and conquer, always have mana pots so you don't have to invest very much in energy (so you can invest a lot more in vitality) and identify your enemies, be carefull of packs like aura enchanted, extra strong, extra fast monsters. Remember you only live once