She was using a well-known expression. The OED says,
P7. to light (also burn) the candle at both ends: to consume or waste in
two directions at once.
Cf. Cotgrave /‘Brusler la chandelle par lex deux bouts’./
1736 N. Bailey et al. /Dictionarium Britannicum/ (ed. 2) (at cited word)
The Candle burns at both Ends. Said when Husband and Wife are both
Spendthrifts.
1753 J. Hanway /Hist. Acct. Brit. Trade Caspian Sea/ II. xlii. 281 Apt
to light their candle at both ends; that is to say, they are apt to consume
too much, and work too little.
1848 C. Kingsley /Saint's Trag./ iii. i. 140 To double all your griefs, and
burn life's candle, As village gossips say, at either end.
I agree that it's not a proverb, but here's the OED again:
2. Used or referred to in a proverb or idiom; familiar or current as a proverb;
notorious, well known, especially so as to be stereotypical.
1571 A. Golding tr. J. Calvin /Psalmes of Dauid with Comm./ (xliv. 14) i.
f. 173/2 The name of them flew comonly abrode among proverbyall figures
[L. proverbiales figuras] in way of reproche.
1589 R. Greene /Menaphon sig. H3 That grounded tranquilitie, which
made it prouerbiall to the world, No heauen but Arcadie.
1711 R. Steele /Spectator/ No. 145. ⁋2 What Hudibras says of such
Disputants, which is so true, that it is almost Proverbial.
1792 H. H. Brackenridge /Mod. Chivalry/ I. i. 7 A Jack of all Trades, is
proverbial of a bungler; and we scarcely ever find any one who excels in
two parts of the same art.
1816 J. T. James /Jrnl. Tour/ ii. 105 The honesty of the Swedes is as
proverbial as that of the Highlanders of Scotland.
1832 F. A. Butler /Jrnl./ 31 Dec. (1835) II. 100 The Baltimore clippers are
proverbial for their elegance and fleetness.
1878 T. H. Huxley /Physiography/ (ed. 2) 45 The proverbial London fog
owes its density and darkness to the smoke.
1937 M. Allingham /Dancers in Mourning/ viii. 108 This morning..the
proverbial monkey-wrench had landed squarely in the middle of the brittle
machinery.
1976 J. Snow /Cricket Rebel/ 19 Having bowled a short ball at a batsman
during one match he sarcastically patted the pitch almost in front of my feet.
This is the proverbial red flag to a fast bowler.
1996 C. Bateman /Of Wee Sweetie Mice & Men/ xxv. 193 Matchitt and the
rest of the camp left under cover of darkness, using the proverbial tradesman's
entrance.
--
Jerry Friedman