Can a dress be lengthened?

Your dress doesn't have any hem detail - it looks like a straight turn up to me - so it's possible there may be an inch of fabric hem to work with. Most of them are cut fairly close though, so it depends on what the person who turned your seller's dress up did with the extra fabric (unless she bought it at that length?).

You might not want it floor length anyway. Mine was slightly shorter.

Perhaps you could add a band of fabric at the bottom? Or add a longer underskirt?

Today I am wearing a skirt thatIi lengthened by 4" as it was far too short to wear to work. I sewed a double band of satin-backed crepe onto the hem of the skirt having removed the previous hem turn up.

So yes, dresses can be lengthened, but it isn't as easy as taking them up. And the "join" will show so you will need some way of concealing it if it bothers you.

PS I have no idea what your dress looks like, so can't comment in any detail.

PPS Satin is a fabric that "bruises" so if you take down a hem the previous line of stitching is likely to be visible whatever you do to it.

I'm not a professional seamstress by any stretch of the imagination, but I do like making clothes.

Lengthening dresses is harder than shortening them. Satin will show if there's fabric to let down, so you'll have a "join" regardless. Your best bet will be having some lace or frippery appliqued over the join to disguise it, but if it's otherwise very plain, it may look a bit odd. If you've got some frippery elsewhere on the dress, a good seamstress will be able to find a close match. Alternatively, having the join embroidered will disguise it, but it'll likely be quite expensive.

Find the best seamstress you can afford. Ask for examples of her previous work. Get one who's used to working with satin; I will not sew using charmeuse because it's a total nightmare to work with (puckering, tearing, marks from pinning, it's slippy...). A seamstress who isn't used to that particular material can utterly destroy a garment with one mistake, and I wish I was exaggerating.

Is it poofy? Having some under layers taken out and minimising the poofiness can make a dress sit lower to the ground.

Thank you all for your help and advice the lady is going to measure the length of the dress tonight and hopefully that'll give me a better idea although I'm now thinking it might just be the perfect length as I measured myself last night.

FTLOMB I hadn't even considered about it not needing to be totally floor length and if it is too short I think we are literally talking an inch so it may be that it doesn't matter if its a teeny bit too short