I have a pair similar to those girlfriend jeans from Mango (too big now though, although I have hacked it by removing the tags and flipping the waist over and down to wear it low rise, sounds odd and a touch makeshift but it works and someone did ask if they were Vetements
), they're called the Slim Boyfriend, they're quite versatile and totally different from the Me + Ems, I'd keep them both if they're flattering not helping.
Edina, I'm going to be controversial and say if you've got the space just hold onto it not helping again, shopping in your own reject bin can be quite the unexpected treasure trove later on. Store it somewhere else with anti-moth protection just to keep your actual wardrobe manageable.
I tend to store my clothes seasonally so everything passes through my hands twice a year (once when storing and then unboxing approx 4x a year) and I usually do a big fitting session (of both the stored stuff and the stuff coming out of storage), paying special attention to the things that didn't get worn (did they just not feel 'right' for the tendencies/silhouettes/colour palette of the moment or is it just the most unflattering thing ever, etc.), check what needs mending, stain removal, specialist cleaning, etc. Anything that I'm not certain of for the nth time, don't feel like mending, washing by hand before storing (knitwear), or doesn't have much wear left in it is easily binned/donated. Because it's a rather tiring exercise you become ruthless by default and it's easy to see what's lacking. I only find it manageable in a 4 seasons approach, I think just S/S and A/W would be too daunting a task.
Expensive regrets can easily be sold on and absolve you from the regret. Vestiaire Collective if it's a good label and you price it well, otherwise eBay.
Waltz, I find jeans sizing a bit all over the place and in my mind Levi's comes in generous these days (testament to the fact that I'm now 2 sizes smaller with them than when I was 12
) and Reiko is TTS for a denim brand but not ridiculously small, so my guess would be go one size up. Their online size guide is pretty accurate. You can also have a look at Cimarron jeans (originally Spanish but now appears to be French
they're a bit more generous in the bum and thigh area) and Lois (actually Spanish). Think Zalando may sell all three, since they do free delivery and returns that may be the easiest, even if it isn't the colour you want, just to fit the different sizes as most French shops are expensive on shipping and returns are rarely free. Otherwise, I think Iris Fashion sells Reiko and they have a few shops in London IIRC and online of course.
Unexpected bargain bonus for me today, when I went to pick up my new Isabel Marant trainers they had been further discounted to 70% and I still had the VIP cash discount voucher so their inability to locate the other shoe last week has saved me quite a bit. They also look great with my new Proenza Schouler trousers, taking down the formality of them a bit, quite pleased to have a pair of white trainers that are actually wearable in winter.