I've heard this before, and it's a source of some discomfort for me as a feminist. On the one hand, I don't like stories where the heroine's main quest is motivated solely by her love interest, or where the purpose of the female character is solely bride/love interest of the hero. On the OTHER hand, I'm currently engaged and have spent my entire life (as have most people, I expect) hoping that I would find a person who would love me as much as I loved them. This is not to say my whole life has been about finding that person and that love, or that I feel I've attained a Happy Ending by doing so. This is only to say that while I don't believe a woman needs love or marriage to be complete or that women who don't marry are somehow less successful as women, I do believe that most people (especially young girls/teens who internalize media in a way that shapes their identity) want to "end up" in love, or at least experience it in some significant way. We're not solitary creatures by nature. And while some people end up perfectly happy and content without partners, very few imagine this as children.
Which means that when we watch movies or read books, if we identify with the heroine, we probably want her to find love in one way or another. We want this for ourself and so we want it for the characters we wish we could be. And I think it is both reasonable and realistic to say that feminists and all women who have goals outside of marriage still largely end up with the opportunity to have a partner and love in their lives (though of course, some choose not to.)
What I think is the more harmful depiction is the emerging dichotomy between feminist characters who don't have love interests and the more traditional princess (or, worse, the faux-feminist Strong Female Characters) who do. Which sends the message to little girls or teens that being pretty will get you the man (or woman) and being smart/witty/brave/kind will not.
As for my own writing. I have two novels, both with female protagonists. The first does not find love, but her arc is more about finding safety and a sense of self. And she certainly finds non-romantic love. But it was very much the set up for a second book which would see her learning to love and allow herself to be loved. This was also a severe Mary Sue and so I didn't feel too badly about leaving her without a romantic interest because I knew she'd turn out all right in the end.
The second book is more complicated. My main character is not a Mary Sue, and begins the book damaged and traumatized and wanting only to escape. The second portion of the book is about her quest for revenge and finally about how she can find a way to live as a whole person. Yes, she has a love interest and yes, there is a wedding. (Actually there are several.) I wanted this for her. She spends so much of the story isolated by her past and her dishonesty and her single-minded ambitions, but while she is flawed she is also intelligent and vulnerable and desiring mostly to do the right thing. To leave her alone (or to kill off her love interest) seemed like punishing her for these things, for not being a well-behaved woman.
But it was not just the affection of author for character that made me keep the wedding at the end. I thought about what I wanted readers who identify with the main character to take away. And what I wanted was this: that the world will try to break you, that it will punish you for defying patriarchy and for refusing to accept what you are told. You may lose people you love, you may suffer tragedy and make mistakes and be betrayed even by the ones who are supposed to protect you. But you will have friends and kind strangers and when it seems too hard to go on, somehow you will find the strength to do so. When you are ready, and when you find someone who sees the strength in you as something to be treasured and not smothered, even if you gave up on the idea and believed you were too old or too broken, love will be there in the end.
Falling in love has made me a better, calmer, stronger person. It has made things I once thought were impossible seem easy. I do not feel it has made me less of a feminist or less of a woman. If I have daughters, I hope that I can find the right way to explain this. That falling in love need not be the sum total of their life, but that it is no trifle, either. That it is not something they will ever have to trade for being smart, strong and independent. That love, and even marriage, with the right partner, is worth working for and fighting for.