I think it would be nice to take some flowers, and probably also to acknowledge that you feel like you should have been there more for her no dig from me there, I'm terrible for being one of those people whose life just gets in the way! And then feeling guilty for neglecting people afterwards.
Of course they can, as can just saying so, and not trying to skirt around the fact. She’s still meeting up with you, so she obviously wants to and isn’t holding a grudge. Don’t be so hard on yourself. for you!
Don't be too hard on yourself. People often get loads of support in the first few days and weeks after a bereavement and then it dwindles. The main thing is to be fully present for her now. Find out what she needs and try to follow up with something that helps eg a bit of company or diversion, or help sorting out practical stuff. Remember that there will be difficult anniversaries ahead and things like sorting out her effects and probate, or family niggles, which can be very draining for someone also dealing with loss. You sound like a lovely friend.
Flowers would be a lovely gesture. Agree with other posters - don't be too hard on yourself. Sometimes life just gets in the way! I often don't get to see or talk to my best mate for months because you blink and the weeks have flown by, especially when you are busy. You have already apologised for not being there when her mum died, so I'd start with a big hug and say it again at the beginning - you are sorry you weren't able to be there for her, but that you are here now and then follow up your meeting with a call or text to say how lovely it was to see her.