1.  Marriage Record:

2.  1870 Census Index/Images (online at Genealogy.com; Image #12 of 86):  New York (Ward 15, District 8), New York Co., NY, Roll 994 (Book 1), p. 597B, PN 12, enumerated 12 Jun 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

52	68	Yarington C J	45	F	W	Keeping House	15,000		Virginia
		Ashburn E.P.	23	F	W	Authoress	5,000		"
		Yarington Emma	21	F	W				"
		De Wersion Bell	19	F	W				"
		"     John	45	M	W	Stock Holder in Banking Estab			"
		Yarington R M	17	M	W	At College			"
		"     John D	15	M	W	At school			"
		De Wersion John	3/12	M	W				"
		Stinner J	49	M	W	Man. of Boots & Shoes	10,000		New York
		Ladd Geo	23	M	W	Patentee			Mass
		Eagan Aurthur	21	M	W	Dry Goods Clk			Ireland
		Peirson Howard	23	M	W	Patentee			Conn
	69	Abbey Horatio	52	M	W	Music Pub	4,000		New York
		"   Cordelia	40	F	W	Dress Maker			"
		"   Gertrude	6	F	W				"
		"   Bessie B	2	F	W				"
		Maguire Mary	20	F	W	Domestic Servt.			Ireland

C. J. YARRINGTON is Arabella's mother.  E. P. ASHBURN appears to be Arabella's widowed/divorced/deserted sister, Eliza Page YARRINGTON.  Richard M. YARRINGTON and John D. YARRINGTON are Arabella's brothers.

3.  LDS.  Family Search: Census Records: 1880 United States (online at FamilySearch.org):

Census Place: New York, New York (Manhattan), New York City-Greater, New York
Source: FHL Film #1254895; NARA Film #T9-0895; Pg 355B
	Relation	Sex	Marr	Race	Age	Birthplace	Occupation	Fa	Mo
Belle D. WORSHAM	Self	F	W	W	28	AL	Keeping House	AL	AL
Arthur M. WORSHAM	Son	M	S	W	10	NY	Scholar	AL	AL
Cathrine YARRINGTON	Mother	F	W	W	61	AL	At Home	AL	AL
William SKEPWORTH	Other	M	S	B	30	VA	Coachman	VA	VA
John HURBERT	Other	M	S	W	30	IRE	Coachman	IRE	IRE
John CASSIDY	Other	M	S	W	30	IRE	Coachman	IRE	IRE
Katie KEENAN	Other	F	S	W	18	NY	Servant	IRE	IRE
Elizabeth CLARK	Other	F	S	W	40	SCOT	Servant	SCOT	SCOT

In the 1900 census, Belle gives her father's birthplace as MD and her mother's as VA.  Clearly, Belle was well off before she married Collis, but then, she'd already been his mistress for about ten years at this point.  "Arthur" should be "Archer."

4.  Stephen Birmingham.  1982.  The Grande Dames.  Simon & Schuster, NY.

Henry Huntington nephew of the late C.P., built Rancho San Marino in the foothills of the San Gabriel Mountains east of Los Angeles to lure his beloved Arabella to the West Coast.  When they eventually married, they assembled at San Marino one of the most important private collections of rare books and art in the world.  Its contents, including Gainsborough's Blue Boy, were to become the Huntington Art Museum.  They lived in the house only a month or so every year.  Where Arabella led, her adoring Henry followed.

5.  Kevin Starr (California State Librarian).  1985. Inventing the Dream: California through the Progressive Era.  Oxford Univ. Press, NY (excerpts online at Friends of California Libraries web site):

Arabella Huntington was a strange, imperious woman, whose aristocratic hauteur (so evident in the portrait of her painted by Sir Oswald Birley in 1924, the year of her death) masked a continued fear of discovery.  She hid her tracks skillfully — no birth certificate, no baptismal record, no marriage license — but it is very probable that before she met Collis P. Huntington she lived in wartime Richmond, Virginia, as the mistress of a gambler and faro banker, one John Archer Worsham, who, after the war, abandoned her (most likely pregnant) in New York City.  In any event, like Scarlett O'Hara, Arabella was a survivor.  A few years later she resurfaced as the mistress, lobbyist, and business advisor of Collis P. Huntington, president of the Central Pacific.  She eventually became his second wife.  Her son Archer was either Huntington's or the result of her early liaison with John Archer Worsham.  By 1900 Arabella Huntington had not only survived, she was one of the richest women in the world...

Starr somewhat overstates his case — for dramatic effect, I presume — because there was no such thing as "birth certificates" until well into the 20th century and, even had she been baptized, few church records survive, nor have all marriage records survived.  In fact, antebellum marriage records in the south are a sad joke amongst genealogists because half the court houses in the south were burned during the Civil War.  In most cases, the best you can do is deduce that a marriage occurred (e.g., by finding a couple in the census).