Tip #1 she's still just a baby let her enjoy playing and don't stress out too much. She will learn them soon enough. My sister's daughter didn't start speaking until 4 and she didn't have any learning disabilities once she did. Some kids are just late bloomers. Truthfully, she may not care much about learning right now. One thing you can do is make sand paper letters and let her feel them. Some kids learn easier with visuals and manipulatives. This is what Montessori uses with children, I used this with my children and they loved it.
Honestly, I'm not trying to be mean, but I think people stress on children learning too much too soon. The best thing you can do to help her learn is spend lots of time with them and read to them every single day. Sit her on your lap and read. Enjoy your time with her while she is young. There will be time to get her help if she does have a learning disability, but I think we as a society push our kids too much too soon. She will get it when she's ready. I have three kids and they all learned differently. Some kids just are very creative and think outside the box. My oldest is an honor student, I have never pushed her to go into honors classes. My middle child I would venture to say is just as smart but she doesn't push herself as much. She is very creative and thinks way outside the box. I encourage them to be themselves, and don't focus on grades because I know testing doesn't really measure intelligence, some are very poor test takers. However, if I see grades dropping and I know they can do the work and are being lazy then I would try to figure out what is going on. Another suggestion is that maybe her eyes need tested. I had to have glasses by kindergarten because I could not see the board. Maybe she is seeing your E as an A because of her eyesight. I know it is hard to test them at this age, but I did take mine in at four. She didn't know her letters yet either, but she knew her sounds and sounded them out for the eye dr.
Sorry, this is so wordy. All of this is just to say, relax and enjoy your child she is still young. Enjoy your time with her. I think reading is the best method of teaching you can ever do for your child. If you point out the words as you read it will start clicking in eventually. And try to give each child the same amount of individual time as you can. We do days out with our children, one on one time with that child only. One Sat. it may be with the oldest one and dad, the next the middle, then the youngest, then I start my turn with the oldest, next weekend with the middle then the youngest. Once I asked one of my children how do you know that we love you. The answer was because you take us on days out and spend time alone with us! I was so shocked and quited excited to hear that. Of course we don't do it every weekend and it has been awhile since we have done it, sometimes a month or so will go by, but it is important to them.
And please don't guage her learning by your eldest. We often compare our children too much too. They all learn so very differently, remember what worked for your oldest may be way off for your second born. They are totally different children and will learn differently. It is way too easy to compare we all do it even when we try not to. You are SO SMART TO QUIT before you are upset and frustrated!!! Keep up the good work, you are a wonderful mom.
Philippians 4: 6 & 7 Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God, and the peace of God will guard your hearts and minds in Christ Jesus." Casting all your cares upon Him for he cares for you." 1 Peter 5:7 These are versus I often need to remind myself because I often get so worried about things instead of trusting God and leaving them in his hands.
Take care and God Bless You.
K.