It completely depends on the brand, the denim, the rise, the inseam, the whole over all fit of the jeans etc just cause one pair didnt look right doesnt mean all of them wont. Im a size 26/27 myself and i always thought i couldnt wear skinnys until i tried on some frankie B skinnys and then Diesel matics in 81m wash, matics and frankie Bs are really the only skinnys i look good in i think, i just look silly in the rest, i only have a 30" inseam as well.
So make her try some diesel matics, 81m wash is the best, i best they will fit her fine and she will look great. If she still isnt comfortable then she should try straight leg cuts to start off with they are just as sexy and make sure the rise isnt to high i wouldnt ever go with a rise over 7.5 for me but i find 6.5 - 7" rises are the best on skinny cuts

I do have sympathy for her i think everyone feels this way sometimes when they are just having a bad day, i get it quite alot its normal.
You seem like a very loving supportive boyfriend too so thats good
