EmmaFrostFiles.com

Rating: -1

According to Emma Frost, herself, yes:

(click image for full scan).

But isn't this is a retcon?
Well...in a sense, no. The writer Grant Morrison decided to add on some extra information into Emma's character. While some fans believe Emma has a faux English accent (she fakes it), Marvel actually delved deeper into the fact that her English accent is genuine:

During the Emma Frost comic, a miniseries that explored her childhood up to college years, Emma met a telepathic British colleague known as Astrid Bloom. Astrid taught Emma the basics of telepathy and even introduced her to world known as "unethical telepathy." Astrid and Emma's relationship eventually became hostile, which lead to a telepathic duke out in the astral plane. Emma ended up as the victorious telepath but ended up killing Astrid in the process.

Fanwank: While both of the inexperienced telepaths duking it out in the astral plane, Astrid's English accent accidentally transferred into Emma's speech patterns through her brain.

Don't ask me to scientifically explain this - I can't. But it's very possible that this is Marvel's reason to how Emma "received" an English accent.

Although, some fans have claimed Emma's family generally had English connotations. It could be very well possible that Emma's English accent started with her family. See, it's hard to tell - because - well, the characters don't talk through audio, rather our through our imaginations.