There is nothing more unattractive than a woman who says she is unattractive.
A woman usually claims she (or that which she is wearing or that which she said or made) is unappealing because, A. she is begging for attention and compliments (“oh no it’s true, you ARE utterly fabulous!”), but is usually because, B. she doesn’t trust and love herself enough. Either way, it’s not charming, it’s not stylish, and it’s not attractive.
Accepting a compliment will not make you look like a snob or self-absorbed. When someone says they like your blouse, thinks you look thin or feels that a certain color is flattering with your skintone just say thank you.
And really mean it.
Be thankful that a person in your world took time from their day to notice you and let you know that they are pleased with what they noticed. Be gracious. No need to go on about how the blouse should have been donated years ago, that you are in desperate need of a root touch-up, that you are so bloated from binging on French fries the night before or that your dress clings to your hips. When you shoot down a compliment with a self-deprecating comment it is as though you are refusing a gift. It is okay to accept that gift, the person wasn’t forced to give it to you, offer your thanks and carry it with you for the day. You deserve it.
And if you want a compliment or a suggestion, stop fishing for one with a self-deprecating comment. Find a good friend and ask that person what they think. How do you really look in that dress? Why do I have a hard time looking good in photographs? Do you think I look better in green or red? Only then will you know if the response is honest, or stated to make you feel better. Trust the feedback from those who care about you, and use it to develop and gain confidence and poise.
And remember, you ARE a fantastic human being! You have wonderful exterior and interior traits that make you unique and charming and loveable. Surround yourself with people and things that make you feel and look good and you will need less self-deprecating comments.