I'm not sure if Woolf means to imply that love can't be found in the world. Indeed, there are many charater's whose marital status may seem bleak or unhealthy, but I think there is more there than just the implication that love is hard to find. This moment in June. She isn't lying- you can tell Mrs. Dalloway is one who loves the cool morning air and soft yellow cats. Good luck, I hope this helps.
Pure love is unattainable.
In Lit Crit, arguing absolutes is not generally good form, let alone an attainable feat. I think that you certainly could write a paper using love in MD as a topic, but you'll want to have a much more focused thesis. Clarissa also has a love for the party and thus the group of invitees as a whole. Expand to a love for society, perhaps, with which she has been disappointed. My apologies for the possible botching of the character names.