Wa alaikum as Salam, 

Thanks for reaching out and we pray Allah (S) continues to increase you in patience and iman. You have already received a great gift in yearning to become closer to Allah (S) and wear hijab! There are many who are never blessed with this bounty. This isn't the first time we've had a question similar to yours, so take comfort in knowing you're not alone. In the Quran, Allah (S) says, 

"Your Lord has decreed, that you worship none save Him, and (that you show) kindness to parents." (Quran, 17:23). Additionally, according to Bukhari and Muslim, the Prophet (S) was asked, "Which work is best?" He replied, "Prayer at its time." He was then asked, "Then which?" He (S) said, "Excellence to parents." They asked, "Then which?" He said, "Striving in the way of Allah (S)."

It is clear Islam places great emphasis on obedience and kindness to parents, in particular our mothers, but more important is our worship and obedience to Allah (S). Obedience to parents is not expected when they ask us to do something that is not in line with or contradicts the teachings of Islam. In this situation, your duty to obey Allah (S) and wear hijab trumps the duty to obey and please your parents. I realize this is a very delicate situation, and one that needs to be dealt with using wisdom, patience and kindness, but know that your ultimate obedience lies with Allah (S). That being said, just because you have the duty to disobey your mother and wear hijab, that does not mean that you no longer have the duty to treat her with respect, love and kindness.

Additionally, know that dealing with this situation, is, in itself, a form of worshiping Allah (S). Your struggle is what is described in the last part of the hadith above, "Striving in the way of Allah (S)." Indeed Allah (S) says in the Quran, 

"Your Lord has said, 'Call me, I will answer you." (Quran, 60:60). Additionally, in a hadith qudsi, the Prophet (S) said, Allah (S) said, "I am as My servant thinks I am. I am with him when he makes mention of Me. If he makes mention of Me to himself, I make mention of him to Myself; and if he makes mention of Me in an assembly, I make mention of him in an assembly better than it. And if he draws near to Me an arm's length, I draw near to him a fathom's length. And if he comes to Me walking, I go to him at speed." (Hadith Qudsi 15, related by Bukhari). 

Do not think that by struggling or striving in the way of Allah (S), He will leave you to fend for yourself. He will be with you, every step of the way, making things easy for you, showering you with His mercy and favoring you. All you need to do is call on Him. Trust in Allah (S), put your hijab on, call on Allah (S) for His help and know that you are doing what is required and expected of you. Inshallah everything else will fall into place.

Now, as for your mother, I suggest you sit down and talk with her. Perhaps she doesn't understand how serious you are and that you've given this much thought. She might think that at such a tender age you don't really know what you want. Let her know you're very dedicated to bettering yourself in order to become closer to Allah (S) and wearing hijab is just a part of that process. Let her see how serious you are about it and that it doesn't matter to you what anybody thinks. Have a heart-felt conversation with her explaining your point of view and the decision you've made. What role does your father play in the equation? Do you have any siblings that can help your cause? Talk to them and see if they can help persuade your Mom based on your serious conviction and desire to please Allah (S). 

Additionally, do not underestimate the power of du'a! The Prophet (S) said, "Du'a is the weapon of the believer." Make du'a Allah (S) softens the heart of your Mom and makes this transition easy on you. Allah (S) says in the Quran, 

"If Allah is your helper, none can overcome you. And if He abandons you, then, who is there to help you after that? In Allah the believers should place their trust." (Quran, 3:160).

Let Allah (S) be your Helper. Place your trust in Him, call on Him and He will not lead you astray. Inshallah with due time, your Mom will see how wearing hijab has made you a better Muslimah, and hopefully a better daughter. Who knows, your actions may even inspire her to wear hijab!

We pray Allah (S) makes this transition easy for you! You are in our thoughts and prayers and always have us to lean on!