I have to say you're doing an amazing job, under the circumstances. With anxiety and shyness, for you to have made some friends is amazing. It really is. Under the circumstances of having a mum who can't help but tell you how brilliant she is, you're doing an amazing job in working to analyse how this is impacting your wellbeing. I imagine you're amazing in other ways too, maybe in ways you don't even realise.
As a mum, I believe one of my roles is 'Leader/guide'. Having experienced depression in the earlier part of my life for a number of years, I am conscious of the need to not just lead in regard to physical wellbeing/health but also mental and spiritual. When I say 'spiritual', I don't mean in a religious sense, more so in a soulful or natural sense.
lillief, if there's one natural skill worth knowing (which I teach my kids) it's the skill of sensing who's depressing, something you can get a feel for. If you can develop this skill, it's of benefit in a couple of ways. First, being able to easily sense who's depressing in a degrading way puts you on alert. You can become alert to the fact such a person is going to bring you down either intentionally or unintentionally. You can be prepared for depressing conversations. Kind of like 'Okay, let's see how many ways you can bring me down. Bring it on, let me count 'em'. It becomes about looking at their lack of filter and inability to inspire. You can take it to a whole new level and even begin to wonder about them, why they lack the ability to inspire. You may even come to question them. The 2nd benefit involves this sense leading you to feel who is inspiring, in comparison. It's like an internal compass. True north feels inspirational, everything going south (people/situations bringing you down) feels depressing.
I mentioned abilities you may not realise you have. I bet you have the abilities of a sensitive/a feeler. These are incredible abilities you can do so much with. Perhaps your mum doesn't possess many of these abilities. I imagine you're far more advanced than her. While developing and mastering your sensitivity can be deeply challenging, a good start can involve taking things from 'What's wrong with me?' to 'What am I sensing in that person?'. Are they depressing you, draining you, agitating you, inspiring you, guiding you toward a constructive path, looking down on you while putting themself on a pedestal etc. Each one has a feel to it.
I believe we're sensitive for good reason :)