Question: Do humans ever act unselfishly, even in love?
Answer: People act unselfishly all the time. Indeed, that is one key to what is wrong with much of the world. It certainly explains why so many love affairs turn out badly.
Objectivism holds that human beings have free will. We choose our actions. We need moral principles because we need to know how we SHOULD choose. Objectivism holds that rational selfishness is objectively good. It is how people should act. But if people did usually act this way, we would not be a radical group, and the Objectivist ethics would just be common sense. Every time a rich person votes for higher taxes, you see unselfish behavior. Every time two people marry because they think their friends and family will approve of their choice, you see unselfish behavior. Right now there is a spate of suicide bombings in the Middle East. That's definitely unselfish, though perhaps more motivated by hate than love.
The question you have asked: "do people ever do X" is a positive question. It asks about what is.
Perhaps you meant to ask a normative question like "Should humans ever act unselfishly, even in love?" This asks about what we should do.
On that issue, I suggest you read Ayn Rand
's Atlas Shrugged
, if you haven't yet. An important theme of that novel is the relationship between love and self-interest. There are subtleties I don't have time to address here.
The short answer is that even love should be selfish. As Ayn Rand
writes in The Fountainhead
, "To be able to say 'I love you,' you have to be able to say the 'I.'"
In Objectivist terms, "selfish" means "concerned with one's own interests." And life and happiness are the basis of one's interests, not mere whim or wish. So Objectivist selfishness is a rational, principled selfishness, not a narrow, cash-and-carry, solipsistic attitude toward others.
Love is a celebration of one's own values embodied in another person. Romantic love (and to some degree any close relationship) also gives one the value of psychological visibility: being to able to see oneself reflected in the response of another. One may value another person so much that one sees oneself threatened by what threatens the beloved, or so much that life is not worth living without that person (that is a theme in Atlas Shrugged
But generally, love is not self-sacrifice. Love is not about giving up oneself, but expanding oneself. Trade, the exchange of value for value, voluntarily and to mutual benefit, should be the guiding principle of all one's relationships. This applies to commercial exchange, but also to the trade of non-material values involved in friendship and love. Self-sacrifice (which is self-destruction) is inimical to trade and to any benevolent relationship among people. It is part of a nauseating moral attitude that loves death and admires most the martyr.