I was wondering if anyone knew of sean-nos songs about love, preferably to be sung by a girl.
Lamenting love is a fine theme too.

Go raibh míle! :)

A great source of songs as Gaeilge is Ceolta Gael 1 & 2,Mercier Press.It comes with a cassette.Seán Og agus Mánus O Baoill,editors.

An raibh tú ar an gcarraig? is a lovely song of unrequited love.Quite short and has lots of repetition.Can't put my hand on the book just now! Maybe another member has the words.

"Dónal Óg" is one of the really big songs about lost love, sung from the point of view of a woman.

Dónall Óg is very old also and beautiful. The following lyrics are from a version sang by Maighread agus Tríona Ní Dhomhnaill, tá sé an deas!

A Dhónaill Óig, is tú pór na ngaiscíoch
Do chúl buí daite na n-ór buí snoite
Is iomaí cor is lúb in do chúl a ghaisce
Is tá grá na mná óga in do chófra i dtaisce

Tá mo ghrása ar thóin an Lagáin
Is ba ghile a thaobh ná aol i gcaisleán
Ba ghlaise a shúil ná drúcht in Aibreán
Is bhí boladh na n-úllaí go cumhra ar a anáil

A Dhónaill Óig, má théann tú thar farraige
mé féin leat is ná déan dom dearmad
Gheobhaidh tú féirín lá aonaigh is margaidh
Is beidh iníon Rí Gréige ina céile leapa agat

Bhain tú thoir agus bhain tú thiar dom
Bhain tú an ghealach gheal agus bhain tú an ghrian dom
Bhain tú an croí istigh i lár mo chléibh dom
Is nach rómhór m'eagla gur bhain tú Dia dom

Here is a link of Seosaimhín Ní Bheaglaoich singing a version of it on the Highland sessions.

http://www.youtube.com/watch?v=Zo9f1Eld8jA

The following version by Maighread Ní Dhomhnaill might be closer to the lyrics you have given, a Bhearnaidín:

http://www.youtube.com/watch?v=umfjYu1Tdfg&feature=related

aye, knew they differed. Go raibh maith agat

Caisleán Uí Néill is another good one for you.
Or (and this is one of my absolute favorites) Bruach na Carra Léith:

Óra, éirigh 'gus cuir fál ar an bpáirc i raibh tú aréir,
Má théann na ba sa bhfásach, nach fánach ar an bhféar
Tá crann i lár na páirce ar a bhfásann bláth séin
Más fíor gur chríon an bláth air, go brách ní fhásfaidh sé.