Yeah, Land's End would work but they're not so trendy like what her friends would have.
I found that buying like a halter style or triangle style that you tie at the neck and back, in like an XL, would work for enough coverage. Of course this only works with separates because an XL bottom would be huge. These are not always easy to find, because a lot of the suits have the "clips" and don't tie in one spot or the other. Oh, and a lot of the ones I found that are this style, if they do have padding it is usually removable. I bought several suits like this at Target in years past, cheap and lots of cute ones and variety. You just have to get over the fact that you have an XL top on.
Macy's does sell a few suits that are bra sizing tops. Not so cheap, but when you can find something that actually fits in an actual store... oh god it is amazing.
I just always found it really hard to buy a suit without trying it on. I hate swimsuit shopping to this day, but once I find one I love, well, I LOVE it!
ETA: I just wanted to add, that I've found suits at various stores through the years. JCPenney, Macy's, Target, Aeropostale, and Old Navy are the last 5 places I've bought suits at. I usually get a few each year. You just have to have persistence and try on everything you like, but also be aware that the majority of them are not going to work.