It is the size of the stitch that can make the hugest of difference - and a large stitch (and sounds like it was possibly a machine job) is easier and HEAPS faster...
I don't know what it looks like - so not sure if it is "normal" or not - depends on the fabric, how many layers and other variables BUT..... They should have DEFINATELY told you if the alteration was going to change how the dress looked.
Ultimately, you now have a dress that does not look like the one you purchased - and personally I'd be making a HUGE fuss about that! You don't want to be upset or stressed about it on the day.
I would talk to the seamstress in person, explain your concerns and see what she says. If she apoligises and says she can fix it (and you feel confident that she can) then let them fix it. For me however, if the seamstress was the slightest bit defensive or saying it can't be fixed, id be taking my dress quick smart to someone else who can. Unless you still have lots of material left - you won't have much room to play with a new hem - so you need to make sure however fixes it this time does it properly - you don't want a mid calf length dress....
On another story - one of the very few alfred angelo dealers in Melbourne (Australia) is also the seamstess at her store. When my bridesmaids were measured seperately, at the last measuring - she declared that jess was the same size as clare. I had close to a fight in the store over this when the dresses were ordered, saying I know 110% that my bridesmaids, and clare and jess are DEFINATELTY not the same size - yes they are both skinny (im a bit cuddly) but clare is super super short, has a small frame, and does have b00bs... Jess, also skinny, is tall, no b00bs and has wide hips and shoulders..... Nope - she was adament that jess (that was there at the time) was the same size as clare.
Trying to work out how she could be so certian that they were the same size (when I know they are not) I suggested that maybe she got the measrements wrong. If jess really is a size 2, then clare (who was not there) would have to be a size 0. Clares measurements must be wrong and that would explain the confusion. It would also even make sense, as previously we were going to get henri josef dresses from somewhere else and the girls were measured in sizes:
clare - 2
jess - 4
sarah - 4
danni - 16
in the alfred angelo dresses she was trying to say
clare 2
jess 2
sarah 4
danni 16
I was trying to tell her that jess is much closer to sarah's size, and there is no way she would fit into any clothes of clares. (clare wears siz aus jeans - jess wears 10 *** of her hips)
She even got narky and really defensive, saying she has been a seamstress for 25 years, she has never gotten measurements wrong etc etc etc...
I brought clare back to be measured to make sure hers was right and eventually gave in - i did not need to have a screaming match in the store... I walked out with her GARUNTEE that she had definately ordered the right sizes and all would be fine.
NEVER EVER AGAIN if I have any doubt will I settle for thier word unless I am 100% confident they are telling the truth and are right. Obviously - when the dress came (3 weeks before the wedding) it was WAY TOO SMALL - she could only just get it done up, couldn't breath, and because she was taller and had hips/shoulders - the dress was way too short - and the bodice that should go to her hips like on the other girls only went to her belly button and looked ridicoulous.
I rang this woman (it was the morning of my hens day) and went OFF. She was still defending herself, saying she'll fix it (you cant make the bodice any longer, and i dont want the other girls in mini skirts to match the lengths either) etc etc... I had another seamstress who was doing my gown at my house who said - no way you could fix that dress. Store owner eventually gave in that it couldn't be fixed - but no refund and no time to get a new dress - so the only thing she could do was order extra material for my new seamstress to try and make the sash on that dress larger to hide the ugly too short bodice and they'd have to be different lengths... sarah and jess swapped dresses too - sarah squeezed into the 2 better than jess did - but the 4 was still too small for jess.
At the time it was awful - but a blessing now I suppose - a few days later the wedding actually had to be cancelled - and thank goodness I didn't have to have my bridesmaids in mismatched dresses. We are now going to WDW to get married and over $1200 worth of unused dresses are sitting in my cupboard.
I should write the store owner a letter (she doesn't know i didnt get married) and tell her we couldn't use the dresses due to her stuff up and say we had to get new ones and demand a refund... had the wedding proceeded it was what we were going to look at doing anyway, with my gown seamstress trying to fix the existing BM dress as a back up.
Anyway - longwinded - but the moral of my story - if they have already stuffed it up once - unless you feel 110% confident in thier ability to fix it - don't let them touch it again. I'd rather count my losses money wise than have them completely wreck it on you - and you can take photo's and get advice and try and get your money back from them later!!! Infact - an independant letter and technical information from a seamstress stating that it was done wrong/badly etc may help you get your money back in the long wrong.
Do you have something like consumer affairs - where you can complain about goods not being as described etc???
She also has a wedding planning business and I just can't believe that she thinks that is acceptable. 
I hope everything works out for you and you get your dress to look the way you want. Nobody should have their dress ruined like that.
