Hiya.I am a young mum & I have 4 kids the eldest is now 7 and I have a 2week old baby. I recently toilet trained my 2 year Old well before the baby was born and she just took to it perfectly. Now 5 months later and a new baby, she is starting to have accidents, well holding it in and then doing a little wee in her knickers each time. She totally understands when I talk to her about why I'm upset with her cuz she's pretty smart and it's almost like it doesn't bother her. So I totally understand your frustration!! Especially when your little one Is wanting to wear knickers etc.
If she is successfully going on the potty/toilet at least twice a day and is wanting to wear knickers and so on I would say she is ready to toilet train. I would suggest talking to her about how wearing big girl knickers comes with big girl responsibilities ( obviously use a word that she will understand) and I have been telling my daughter how happy it makes me when she gets her wees in the toilet. I ask her where do our wee wees go? And she says in the toilet so I know she understands what I'm asking of her, and she knows what I expect. Keep up with it, I'm sure all of a sudden it will just happen. But keep consistent. U may have to keep taking her to the toilet often to start with but it will all b worth it! Hope that helps, even just a lil bit smile