dear Uncle, pls help on accident related issues

Dear Uncle,
My Girlfriend and I went for a go-karting event whereby we were asked to sign a letter of indemnity. During the drive, a lady who drove go-Karting car hit my gf's car and she (my gf) got minor injuries as a result.

The lady who was liable agreed to pay us for the medical bill but now they are not going to pay quoting that we've signed the letter of indemnity which sets them free of any liability (while I reckons that).

Would you mind help look at part of the indemnity form we signed at the accident's day? Thanks a million.
Is the third party participant (not the event holder) be held liable for my gf's medical expenses?

I release, waive, discharge, hold harmless and indemnify Kartright from any and all claims or actions for any injury or death to myself, my driver(s), mechanic(s) and/or any person(s) and any loss or damage to any property which may arise out of or in connection with any entry or my taking part in any Karting event or Kart practice sessions, regardless of how that injury, death, damage or loss occurs, even if (by way of example) it happens as a result of:
- the negligence or recklessness of someone else (including Kartright).
- the design, construction, condition, adequacy or suitability of the Karts, tracks, equipment, land, buildings, carparks, paths, landscaped areas or other facilities at the Karting premises.
- any omission, inadequacy or error in any (a) training or instructions that I am or anyone else is given, or (b) in any rules or regulations made or procedures adopted by Kartright.

4. I also accept liability for and will indemnify Kartright against any claims or actions for any injury or death to any person(s) and any loss or damage to property which arises out of my negligence or recklessness while I am at the Karting premises.

5. I further undertake not to make any claim or demand whatsoever against Kartright and/or any of the participants in and in respect of any Karting events organised by Kartright.