solidaritysoul, hi. Welcome to Connect. I so like your question. Like Colleen, I see loving yourself as having very different meanings. I like your mom giving this advice, but your question, even more than deserving an answer, is a brilliant response.
Loving yourself can be taking care of yourself by making sure that you take in food with an interest in your health, exercising, getting enough sleep, taking time and care with hygiene and seeking medical care, studying intently, learning a skill that will keep you both independent and powerful enough to help other people.
When you care for others, you'll become someone who likes themselves, which seems to me quite different than loving oneself.
I think the path to liking who you are and to happiness is to be aware of and kind to others.
You might start with your mom. Make a list of the things that she likes. Think of ways that you can make her days a little easier. It isn't so easy to raise a teenager, Keep talking to her about these ideas of liking oneself.
One more thing to be aware of is that hormones start to shift around at around the age of fifteen and can create an emotional turmoil that is difficult to anticipate.
Bless your life with goodness.

What mascarades as love is self indulgence in things that are in the end self destructive and often not healthful for others in our lives.